A Systematic Review of Treatment Outcomes for Children With Childhood Apraxia of Speech Purpose To present a systematic review of single-case experimental treatment studies for childhood apraxia of speech (CAS). Method A search of 9 databases was used to find peer-reviewed treatment articles from 1970 to 2012 of all levels of evidence with published communication outcomes for children with CAS. Improvement ... Review Article
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Review Article  |   August 01, 2014
A Systematic Review of Treatment Outcomes for Children With Childhood Apraxia of Speech
 
Author Affiliations & Notes
  • Elizabeth Murray
    University of Sydney, New South Wales, Australia
  • Patricia McCabe
    University of Sydney, New South Wales, Australia
  • Kirrie J. Ballard
    University of Sydney, New South Wales, Australia
  • Disclosure: The authors have declared that no competing interests existed at the time of publication.
    Disclosure: The authors have declared that no competing interests existed at the time of publication.×
  • Correspondence to Elizabeth Murray: Elizabeth.murray@sydney.edu.au
  • Editor: Carol Scheffner Hammer
    Editor: Carol Scheffner Hammer×
  • Associate Editor: Ken Bleile
    Associate Editor: Ken Bleile×
Article Information
Speech, Voice & Prosodic Disorders / Apraxia of Speech & Childhood Apraxia of Speech / Research Issues, Methods & Evidence-Based Practice / Review Article
Review Article   |   August 01, 2014
A Systematic Review of Treatment Outcomes for Children With Childhood Apraxia of Speech
American Journal of Speech-Language Pathology, August 2014, Vol. 23, 486-504. doi:10.1044/2014_AJSLP-13-0035
History: Received March 27, 2013 , Revised July 7, 2013 , Accepted December 1, 2013
 
American Journal of Speech-Language Pathology, August 2014, Vol. 23, 486-504. doi:10.1044/2014_AJSLP-13-0035
History: Received March 27, 2013; Revised July 7, 2013; Accepted December 1, 2013
Web of Science® Times Cited: 7

Purpose To present a systematic review of single-case experimental treatment studies for childhood apraxia of speech (CAS).

Method A search of 9 databases was used to find peer-reviewed treatment articles from 1970 to 2012 of all levels of evidence with published communication outcomes for children with CAS. Improvement rate differences (IRDs) were calculated for articles with replicated (n > 1), statistically compared treatment and generalization evidence.

Results Forty-two articles representing Phase I and II single-case experimental designs (SCEDs; n = 23) or case series or description studies (n = 19) were analyzed. Six articles showed high CAS diagnosis confidence. Of the 13 approaches within the 23 SCED articles, treatments were primarily for speech motor skills (n = 6), linguistic skills (n = 5), or augmentative and alternative communication (n = 2). Most participants responded positively to treatment, but only 7 of 13 approaches in SCED studies reported maintenance and/or generalization of treatment effects. Three approaches had preponderant evidence (Smith, 1981). IRD effect sizes were calculated for Integral Stimulation/Dynamic Temporal and Tactile Cueing, Rapid Syllable Transition Treatment, and Integrated Phonological Awareness Intervention.

Conclusions At least 3 treatments have sufficient evidence for Phase III trials and interim clinical practice. In the future, efficacy needs to be established via maintenance and generalization measures.

Childhood apraxia of speech (CAS) is a developmental disorder of speech motor planning and/or programming (American Speech-Language-Hearing Association [ASHA], 2007). It is also known as developmental verbal dyspraxia in the United Kingdom (excluding being the result of any known neurological disorder) and has previously been called developmental apraxia of speech and dyspraxia. CAS causes reduced speech intelligibility because of a hypothesized impairment in the “transformation of an abstract phonological code into motor speech commands” (Terband, Maassen, Guenther, & Brumberg, 2009, p. 1598). Such impairment leads to the current consensus-based core CAS features of “(a) inconsistent errors on consonants and vowels in repeated productions of syllables or words, (b) lengthened and disrupted coarticulatory transitions between sounds and syllables, and (c) inappropriate prosody, especially in the realization of lexical or phrasal stress” (ASHA, 2007, p. 4).
Although impaired movement planning and programming are considered to underlie CAS, there are also reports of disrupted development of speech perception, language, and phonology (including phonological awareness) in children with CAS (Groenen, Maassen, Crul, & Thoonen, 1996; Lewis et al., 2004; Maassen, Groenen, & Crul, 2003). It is unclear whether these are primary deficits or flow-on effects from CAS, comorbid impairments, or perhaps compensatory behaviors, as children with CAS develop their linguistic, phonological, and motor skills concurrently (Alcock, Passingham, Watkins, & Vargha-Khadem, 2000; Marion, Sussman, & Marquardt, 1993; Ozanne, 2005). Children with CAS can therefore present with a range of difficulties requiring therapy from speech-language pathologists (SLPs; Royal College of Speech and Language Therapists, 2011).
The long-term functioning of people with CAS is largely unreported. The available longitudinal studies suggest that CAS is a persistent disorder that requires therapy (Hall, Jordan, & Robin, 1993; Jacks, Marquardt, & Davis, 2006; Stackhouse & Snowling, 1992). Children with CAS, like others with persistent speech sound disorder, are also at risk for literacy, academic, social, and vocational difficulties (e.g., Lewis et al., 2004; Moriarty & Gillon, 2006).
A Cochrane systematic review, a subsequent journal article, and a treatment review have reported no published randomized controlled trials (RCTs) or nonrandomized controlled trials (NRCTs) for any intervention for CAS (Morgan & Vogel, 2008, 2009; Watts, 2009). Despite this lack of high-level evidence, many published articles on the treatment of CAS could facilitate practice and could help identify potential lines of further research. Narrative reviews have identified a range of treatment methods for children reported to have CAS, likely reflecting the diversity of symptoms seen in these children and potentially the research and clinical interests of the authors (ASHA, 2007; Strand & Skinder, 1999). They encompass motor treatments (including electropalatography), linguistic approaches, augmentative and alternative communication (AAC), or some combination thereof (ASHA, 2007; Gillon & Moriarty, 2007; Hall, 2000; Morgan & Vogel, 2008). Few of these lower level treatment studies have been examined rigorously, as they were excluded on the basis of quality in previous systematic reviews (Morgan & Vogel, 2008; Watts, 2009). Provision of recommendations regarding which treatments have supportive evidence has therefore not been possible (ASHA, 2007; Morgan & Vogel, 2008; Pannbacker, 1988). This article presents a systematic review of all levels of evidence that may be critical to inform clinical practice until high-level evidence becomes available.
Two primary challenges face a systematic review of intervention for CAS. The first challenge is in identifying the rigor of each study in terms of research phase (Robey, 2004), the research design, the levelof evidence generated (ASHA, 2004; Perdices et al., 2006), as well as the level of certainty that the effects reported for a given treatment approach are real (Smith, 1981). Treatment research often follows a developmental pathway that is associated with increasing research rigor and different research questions. Robey (2004)  defined five phases in a research program. Phase I and Phase II studies represent pilot or feasibility studies seeking to determine whether effects justify more rigorous study. These can generate Level III or Level IIb evidence (ASHA, 2004; Perdices et al., 2006). Level III evidence constitutes quasi-experimental group (case series) or single case reports with pre- to posttreatment measurement and no within-subject comparison or control conditions. Level IIb evidence comes from more rigorous single-case experimental designs (SCEDs) that systematically apply and withdraw treatment and establish control using a stable baseline phase or limited change in control conditions (Byiers, Reichle, & Symons, 2012; Olswang & Bain, 1994; Perdices & Tate, 2009).
The second challenge is that there is not yet a validated assessment tool for diagnosing CAS. Thus, before evaluation of the treatment in any intervention study, the descriptions of participants must be scrutinized to determine the level of confidence in the authors' diagnosis. This involves determining to what extent the participants are described as meeting the three consensus-based core features of CAS listed earlier (ASHA, 2007).
Smith's (1981)  level of certainty hierarchy considers the research design and the possible effects of the intervention to provide an overall judgment on how likely the results are to be true. For the CAS literature, this can also be extended to include confidence in diagnosis. SCEDs can show early evidence for an intervention, with results from such studies being classed as suggestive or “possibly true.” However, statistically compared outcomes from SCEDs with confident CAS diagnoses, replication (n > 1), and evidence of both treatment effects and generalization of treatment effects could be considered preponderant evidence or “probably true.” SCED designs are usually designated as Phase II and Level IIb evidence (but see Hegde, 2007; Kearns & de Riesthal, 2013). Currently, Phase III studies (Robey, 2004) are typically RCTs and NRCTs. These generate Level IIa evidence using groups of participants to reduce bias and to eliminate individual variance as a factor in treatment success. It is only through meta-analyses and systematic reviews of several Phase III studies of a given treatment approach, coupled with Phase IV effectiveness studies in real-world clinical situations, that results can be defined as conclusive or “undoubtedly true” (Smith, 1981). As all studies of CAS treatments to date are classified as Phase I and Phase II, the goal of this review is to identify treatment approaches with suggestive or preponderant evidence.
Central to this review is treatment efficacy. Efficacy considers clinical cause-and-effect relationships between the provision of intervention and change in participant behavior (e.g., McReynolds & Kearns, 1983; Olswang & Bain, 2013). Demonstration of efficacy extends beyond treatment effects, requiring assessment of maintenance and generalization of treatment effects that signify instrumental change. Response generalization evaluates a child's performance on untrained items that are somehow related to trained items, to determine whether more widespread change is occurring (Olswang & Bain, 1994). Stimulus generalization assesses performance on untrained materials, people, or settings/environments (Olswang & Bain, 1994). Such change is necessary to meet the overall goals of an intervention.
Aims
This systematic review evaluated studies of intervention, published between 1970 and October 2012, that state an intention to treat children with CAS. The aims fall into four broad areas:
  1. Study quality: to describe for each identified study the research phase, the level of evidence, and the level of confidence in CAS diagnosis;

  2. Treatment procedures: to define the behavioral goals and structure of treatment (e.g., intensity and dosage according to Warren, Fey, & Yoder, 2007) for each SCED study (at/above Level IIb evidence) and to group similar treatment types to facilitate treatment outcome analysis;

  3. Treatment outcomes: to examine reported treatment, maintenance, and generalization outcomes; and

  4. Certainty of evidence: to determine the level of certainty for each treatment approach (Smith, 1981) and to determine the effect size for any intervention approach classed as having preponderant evidence.

Method
Systematic Search Strategy
The search strategy used follows Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) search guidelines (Moher, Liberati, Tetzlaff, & Altman, 2009). The flow diagram of study selection is presented in Figure 1.
Figure 1.

Flow diagram of study selection (adapted from Preferred Reporting Items for Systematic Reviews and Meta-Analyses [PRISMA]; Moher et al., 2009). CAS = childhood apraxia of speech; Ax = assessment; Dx = diagnosis; RCT = randomized controlled trial; NRCT = nonrandomized controlled trial; SCED = single-case experimental design; AAC = augmentative and alternative communication.

 Flow diagram of study selection (adapted from Preferred Reporting Items for Systematic Reviews and Meta-Analyses [PRISMA]; Moher et al., 2009). CAS = childhood apraxia of speech; Ax = assessment; Dx = diagnosis; RCT = randomized controlled trial; NRCT = nonrandomized controlled trial; SCED = single-case experimental design; AAC = augmentative and alternative communication.
Figure 1.

Flow diagram of study selection (adapted from Preferred Reporting Items for Systematic Reviews and Meta-Analyses [PRISMA]; Moher et al., 2009). CAS = childhood apraxia of speech; Ax = assessment; Dx = diagnosis; RCT = randomized controlled trial; NRCT = nonrandomized controlled trial; SCED = single-case experimental design; AAC = augmentative and alternative communication.

×
Identification
Nine databases related to speech-language pathology were comprehensively searched for peer-reviewed journal articles. These were Allied and Complementary Medicine, Cumulative Index to Nursing and Allied Health Literature, Evidence-Based Medicine Reviews–Cochrane Database of Systematic Reviews, Education Resources Information Center, Linguistic Language Behavior Abstracts, Medline, PsycINFO, Scopus, and speechBITE. Specific search terms varied on the basis of each database catalogue of terms in its search directories. Key words used were as follows: “apraxia” or “dyspraxia” or “childhood apraxia of speech” and “child*” or “develop*” and “motor speech therapy” or “interven*” or “treat*” or “speech therapy/pathology” or “efficacy” or “evaluation” or “effect” and “speech” or “communication” or “language” or “articulation impairments” or “speech impairments” or “speech disorders” or “speech intelligibility” or “prosody.” A total of 1,301 studies were identified from database searches.
Screening
All references were exported to EndNote X5 (Thomson Reuters, 2011), where duplicates were removed. References were also screened to ensure that authors stated an intention to treat children with CAS (using synonyms; e.g., developmental verbal dyspraxia). Thus, references were searched by title, abstract, and key words in EndNote X5 and were excluded if treatment articles involved other diagnoses without reference to CAS: “cerebral palsy,” “dysarthria,” “cleft palate,” “swallowing,” “ataxia,” “cochlear implants,” “deaf,” “stutter,” “fluency,” “acquired,” “Down syndrome,” “autism,” “phonolog*,” and “gait apraxia.” All references that related to assessment, diagnosis, or description/exploration of symptoms were excluded. Of the intervention articles that remained, the intervention names and authors were searched again in all the above databases as well as Google Scholar to ensure that all relevant articles were found. The reference lists of all review articles obtained were also searched to find any additional articles. Screening removed 913 articles, leaving 119 to be assessed for eligibility.
Eligibility
Copies of articles were obtained and assessed against the final inclusion criteria before being reviewed. These criteria were as follows: (a) peer-reviewed articles published between 1970 and October 2012; (b) in English (to allow analysis by monolingual English speaking authors); (c) treating at least one child/adolescent under 18 years of age with CAS or suspected CAS; and (d) reporting quantitative participant data outcomes focused on speech (i.e., articulation, phonology, prosody, intelligibility, rate), communication (i.e., pragmatics, social communication, AAC use), or language (i.e., phonology, phonological awareness, grammar, morphology, receptive or expressive language, reading, spelling or writing). There was no exclusion on the basis of the type of therapy provided or who provided it. All named and unnamed interventions were included, as were all levels of evidence, except for systematic reviews, as they do not contain individual participant data (ASHA, 2004). This yielded 42 articles for review. Intrarater reliability (first author) for inclusion of these studies was 96% (n = 1,032) with >2 months between assessments. Interrater reliability with an independent rater was 91% (see Supplemental Appendix 1 in the online supplemental materials for the list of excluded articles and reason for exclusion). Raters were not blinded to article title or authors, and raters did not review their own publications. Excluded articles were not further analyzed.
Finally, an additional search was undertaken for other documents, such as published treatment manuals and theoretical or opinion articles on the individual treatment approaches, to confirm the type of behavior(s) targeted (e.g., speech motor or phonological), cues, and stimuli used. This search used reference lists of already identified articles as well as database and Google searches using intervention names and key authors as search terms.
Data Analysis
Review of studies for Aims 1, 3, and 4 was based on information provided in each article (e.g., Moseley, Herbert, Maher, Sherrington, & Elkins, 2008). In one case, only group data were published, and we contacted an author (Brigid McNeill) for individual data (from McNeill, Gillon, & Dodd, 2009a). Addressing Aim 2 at times required reference to treatment manuals and other publications describing a treatment's theoretical framework.
Aim 1: Study Quality
Each study was assigned to a phase of research (Robey, 2004), from Phase I to Phase V. The experimental design and level of evidence were defined on the basis of published guidelines (ASHA, 2004; Perdices et al., 2006). In addition, confidence in CAS diagnosis was assessed as detailed below.
Confidence in CAS diagnosis. A 5-point rating scale was used to rate confidence in CAS diagnosis (see Table 1; Wambaugh, Duffy, McNeil, Robin, & Rogers, 2006). This was based on description of primary versus nondiscriminative features (McCabe, Rosenthal, & McLeod, 1998; see the online supplemental materials, Supplemental Table 1). Primary features were the three consensus-based features listed in ASHA's (2007)  technical report, hypothesized to represent impaired speech motor planning and/or programming. Nondiscriminative features were those shared with other disorders, such as poor intelligibility, slow progress, or delayed language (ASHA, 2007; McCabe et al., 1998). Clear cases of comorbid disorders were also noted, such as receptive language impairment or dysarthria. On the basis of this analysis, participants were classified either as CAS only or as CAS+, in which CAS was the primary diagnosis, but other disorders were present. A rating of 1 indicated high confidence in CAS diagnosis, and a rating of 5 indicated no confidence. Intrarater reliability (first author) on four judgments (presence of each of the three primary features and CAS diagnosis) for 83/83 children studied was 94%. Interrater reliability between the first and second authors for a random 33/83 children was 91%. Discrepancies were resolved by consensus.
Table 1. Five-point rating scale of confidence in diagnosis of CAS (adapted from the Academy of Neurologic Communication Disorders and Sciences guidelines; Wambaugh et al., 2006).
Five-point rating scale of confidence in diagnosis of CAS (adapted from the Academy of Neurologic Communication Disorders and Sciences guidelines; Wambaugh et al., 2006).×
Level Primary characteristics Nondiscriminative characteristics Comorbidity
Level 1 All the primary characteristics were described as follows: CAS was the primary diagnosis described. Any characteristics that were attributable to other disorders may have been described but were not used to diagnose CAS. CAS without another comorbid disorder was reported (excluding expressive language delay).
 • Inconsistency and
 • Lengthened and disrupted coarticulatory transitions between sounds and syllables and
 • Inappropriate prosody.
Level 2 All the primary characteristics were described as follows: CAS was the primary diagnosis described. Other characteristics attributable to other disorders (e.g., dysarthria) were described and may have been used to diagnose CAS. This includes the following:
 • Inconsistency and  • CAS without another comorbid disorder (excluding expressive language delay) or
 • Lengthened and disrupted coarticulatory transitions between sounds and syllables and  • Clear cases of comorbid CAS, in which CAS was the primary diagnosis.
 • Inappropriate prosody.
Level 3 Two of the three primary characteristics were described: CAS was described. Other characteristics that were attributable to other disorders (e.g., dysarthria) were described and may have been used to diagnose CAS. This includes the following:
 • Inconsistency and/or  • CAS without another comorbid disorder or
 • Lengthened and disrupted coarticulatory transitions between sounds and syllables and/or  • Clear cases of comorbid CAS, in which CAS was the primary diagnosis or
 • Inappropriate prosody.  • Cases of CAS in which another comorbid disorder had the same severity (e.g., language delay, dysarthria).
Level 4 Only one of the three primary characteristics was reported, or incomplete/inadequate description of the primary characteristics of CAS was provided. Other characteristics that were attributable to other disorders may have been described, and it is unclear whether these were used to diagnose CAS. Unclear whether CAS was the primary diagnosis.
Level 5 Diagnosis of CAS was reported or implied, but no primary characteristics were described. Unclear whether CAS diagnosis was likely and/or whether CAS was the primary diagnosis. Other comorbid disorders may be present.
Table 1. Five-point rating scale of confidence in diagnosis of CAS (adapted from the Academy of Neurologic Communication Disorders and Sciences guidelines; Wambaugh et al., 2006).
Five-point rating scale of confidence in diagnosis of CAS (adapted from the Academy of Neurologic Communication Disorders and Sciences guidelines; Wambaugh et al., 2006).×
Level Primary characteristics Nondiscriminative characteristics Comorbidity
Level 1 All the primary characteristics were described as follows: CAS was the primary diagnosis described. Any characteristics that were attributable to other disorders may have been described but were not used to diagnose CAS. CAS without another comorbid disorder was reported (excluding expressive language delay).
 • Inconsistency and
 • Lengthened and disrupted coarticulatory transitions between sounds and syllables and
 • Inappropriate prosody.
Level 2 All the primary characteristics were described as follows: CAS was the primary diagnosis described. Other characteristics attributable to other disorders (e.g., dysarthria) were described and may have been used to diagnose CAS. This includes the following:
 • Inconsistency and  • CAS without another comorbid disorder (excluding expressive language delay) or
 • Lengthened and disrupted coarticulatory transitions between sounds and syllables and  • Clear cases of comorbid CAS, in which CAS was the primary diagnosis.
 • Inappropriate prosody.
Level 3 Two of the three primary characteristics were described: CAS was described. Other characteristics that were attributable to other disorders (e.g., dysarthria) were described and may have been used to diagnose CAS. This includes the following:
 • Inconsistency and/or  • CAS without another comorbid disorder or
 • Lengthened and disrupted coarticulatory transitions between sounds and syllables and/or  • Clear cases of comorbid CAS, in which CAS was the primary diagnosis or
 • Inappropriate prosody.  • Cases of CAS in which another comorbid disorder had the same severity (e.g., language delay, dysarthria).
Level 4 Only one of the three primary characteristics was reported, or incomplete/inadequate description of the primary characteristics of CAS was provided. Other characteristics that were attributable to other disorders may have been described, and it is unclear whether these were used to diagnose CAS. Unclear whether CAS was the primary diagnosis.
Level 5 Diagnosis of CAS was reported or implied, but no primary characteristics were described. Unclear whether CAS diagnosis was likely and/or whether CAS was the primary diagnosis. Other comorbid disorders may be present.
×
Exclusions. Articles that lacked experimental control (Level III evidence; n = 19) were excluded, as they could not be used to determine treatment outcomes. The remaining 23 Level IIb articles were analyzed to address Aims 2, 3, and 4. No articles were excluded because of confidence in CAS diagnosis; however, confidence in CAS diagnosis was a factor in determining certainty of evidence—see Aim 4 below.
Aim 2: Treatment Procedures
Articles designed with adequate experimental control (see Aim 1 above) were analyzed descriptively regarding the nature of the treatment. Using the stated treatment goals, selected stimuli, and specific cueing strategies reported, treatments were categorized as primarily (a) motor, (b) linguistic/phonological (including literacy), or (c) AAC (ASHA, 2007; Gillon & Moriarty, 2007; Hall, 2000; Martikainen & Korpilahti, 2011). The structure of treatment delivery was also determined (Warren et al., 2007), including dose (trials per session), dose frequency (number of times a dose is provided over days or weeks), and total intervention time (number of sessions). When reported, home practice and service delivery model were documented.
Aim 3: Treatment Outcomes
Reported treatment, maintenance, and generalization outcomes for each intervention were analyzed for (a) number of participants with a treatment gain (change immediately after treatment compared with baseline); (b) assessment measures and statistics used in determining treatment effects; (c) maintenance of treatment gains at least 2 weeks posttreatment, from report or by comparing treatment data with performance in maintenance probes; (d) response generalization data, when statistical analysis was used; and (e) stimulus generalization data.
Aim 4: Certainty of Evidence
Smith's (1981)  three levels of certainty were applied, on the basis of design (i.e., level of evidence, research design, confidence in CAS diagnosis, and statistical comparison) and possible effects of the intervention/outcomes. A treatment approach was categorized as having preponderant evidence when it showed Level IIb or better evidence (SCEDs), replicated cases, diagnostic confidence ratings of 1–3, statistically significant treatment and generalization effects (or at least moderate effect sizes), and clear maintenance of treatment gains at least 2 weeks posttreatment. Any Level IIb or better evidence that did not meet all the above criteria received the lowest rating of suggestive evidence.
For studies with preponderant evidence, effect sizes were calculated using improvement rate difference (IRD [also known as risk difference]; Parker, Vannest, & Brown, 2009), a valid and reliable tool for SCEDs used frequently in medical research. This method utilizes visual analysis and has reduced assumptions in comparison with other effect size calculations allowing use over a range of SCED designs. It is more discriminative to change than other nonoverlap techniques (e.g., percentage of nonoverlapping data) and is at least moderately correlated with commonly used effect sizes (Parker et al., 2009). An IRD is the difference between the improvement rates of the treatment and baseline/withdrawal/maintenance phases. The improvement rate was calculated for each phase by determining the number of improved points in each phase (those exceeding the data points of the adjacent phase) divided by all the data points of the phase (Parker et al., 2009). Thus, an IRD eliminates overlap across phases in its determination of effect size.
IRDs were determined for treatment effects for each participant and each behavior within an article. The IRDs were then averaged across participants for the treated behavior(s) to determine an omnibus IRD for each article, as per Parker et al. (2009), with 95% confidence intervals determined using WinPEPI (Abramson, 2011). Effects for each article were averaged again to determine an omnibus IRD for a given treatment approach.
IRDs were also calculated for generalization effects for each participant and each behavior/condition within an article. No further omnibus IRDs were determined for generalization because of the various and often heterogeneous measures used.
Results
Aim 1: Study Quality
The 42 studies that met the inclusion criteria were classified as Phase I or Phase II. Of these, 23 represented Level IIb evidence (SCEDs), and 19 represented Level III evidence (one quasi-experimental case series and 18 case reports or descriptions; see Figure 1). There was a shift toward higher quality single case studies over time, with six Level IIb and 12 Level III articles prior to 2006, and with 17 Level IIb and five Level III articles from 2006 to 2012. No RCT or NRCT designs have been published to date.
Overall, there were 83 participants across the 42 single case studies. Within the 23 SCED articles, 32 participants were reported to have CAS, and 19 participants were reported to have comorbid CAS (CAS+). Of the 23 articles, four articles (17.4%) received a Level 1 rating for high confidence in diagnosis, two articles (8.7%) received a Level 2 rating for clear cases of CAS with comorbid disorders, seven articles (30.4%) received a Level 3 rating, seven articles (30.4%) received a Level 4 rating, and three articles (13.0%) received a Level 5 rating for no confidence (see Table 2).
Table 2. Research design, level of evidence, participant description, and diagnosis analysis of the 23 Level IIb (SCED) articles.
Research design, level of evidence, participant description, and diagnosis analysis of the 23 Level IIb (SCED) articles.×
Intervention name/approach Published articles Research design Level of evidence Participant description Diagnosis Diagnostic confidence rating
Aided AAC modeling Binger and Light (2007)  Multiple baseline across 3 participants SCED IIb 2/5 (4;2 [years;months] and 4;4, male, had previous SLP) Severe CAS+ (GDD) 4 (dysprosody and sequencing NR)
Binger, Kent-Walsh, Berens, Del Campo, and Rivera (2008)  Multiple baseline across probes SCED IIb 1/3 (3;4, female, previous SLP NR) Severe CAS+ (suspected VCFS with profound VPI) 4 (dysprosody and inconsistency NR)
Binger, Maguire-Marshall, and Kent-Walsh (2011)  Multiple baseline across 3 participants SCED IIb 1/3 (6 years, female, previous SLP NR) Severe CAS+ (receptive and expressive LD) 5
Articulation with facilitative vowel contexts Stokes and Griffiths (2010)  ABA single case design IIb 1 (7 years, male, 1 year previous SLP) Mild SSD (Hx of CAS) 4 (dysprosody and nconsistency NR)
Combined intraoral stimulation, Electropalatography (EPG) with NDP Lundeborg and McAllister (2007)  ABABABABA single case design IIb 1 (5;1, female, 1.50 years previous SLP) Severe CAS 3 (dysprosody NR)
Combined melodic intonation therapy (MIT) and touch cue method (TCM) Martikainen and Korpilahti (2011)  Multiple baseline across participants SCED IIb 1 (4;7, female, 1 year previous SLP) Severe CAS 1
Combined stimulability (STP) and modified core vocabulary (mCVT) Iuzzini and Forrest (2010)  Multiple baseline SCED IIb 4 (3;7–6;10, 2 males, 2 females, previous SLP for 3/4) Severe CAS 4 (dysprosody and sequencing NR)
Computer-based Harris, Doyle, and Haaf (1996)  Multiple baseline across discourse contexts SCED IIb 1 (5 years, male, approximately 3 years previous SLP) Severe CAS+ (Hx OME, receptive and expressive LD) 3 (dysprosody NR)
Integral Stimulation/Dynamic Temporal and Tactile Cueing (DTTC) Strand and Debertine (2000)  Multiple baseline SCED IIb 1 (5 years, female, 4 years previous SLP) Severe CAS (Hx of VPI) 1
Strand, Stoeckel, and Baas (2006)  Multiple baseline SCED IIb 4 (5;5–6;1, all male, 2–4 years previous SLP) Severe CAS+ 4 (for all cases; dysprosody and inconsistency NR, clearly comorbid)
(2 with mild spastic and/or ataxic dysarthria, 1 with mild intellectual disability, and 1 with OME)
Baas, Strand, Elmer, and Barbaresi (2008)  Multiple baseline SCED IIb 1 (12;8, male, 10 years previous SLP) Severe CAS+ (CHARGE syndrome intellectual disability) 5
Edeal and Gildersleeve-Neumann (2011)  AB—alternating treatments single design (with three stable baselines) IIb 2 (6;2 and 3;4, male, 1–4 years previous SLP) 6;2—severe CAS+ (repaired CLP, severe receptive LD), 1
3;4—severe CAS
Maas and Farinella (2012)  Multiple baseline SCED IIb 4 (5;0–7;9, 2 females, 2 males, previous SLP NR) CAS001—moderate–severe CAS; 3 (by consensus); CAS001 = 1, CAS002 = 3 (dysprosody NR, clearly comorbid), CAS005 = 2 (clearly comorbid), CAS010 = 4 (inconsistency and coarticulation NR, clearly comorbid)
CAS002—severe CAS+ (dysarthria);
CAS005—moderate–severe CAS+ (dysarthria and receptive LD); CAS010—mild-moderate CAS+ (sensory processing, fine and gross motor skill delay, hypotonia, moderate–severe receptive LD)
Maas, Butalla, and Farinella (2012)  Multiple baseline SCED IIb 4 (3 in common with Maas & Farinella, 2012) CAS001; 2 (by consensus); as above and CAS012 = 2 (clearly comorbid)
(5;4–8;4, 2 females, 2 males, previous SLP NR) CAS002;
CAS005—see above;
CAS012—CAS+ (moderate–severe receptive LD, Hx OME)
Integrated Phonological Awareness Intervention (N = 5) Moriarty and Gillon (2006)  Multiple baseline SCED IIb 3 (6;3–6;10, 2 males, 1 female, up to 2 years previous SLP) Male 1—Severe CAS+ (receptive and expressive LD); Male 2—Severe CAS+ (receptive and expressive LD); Female—mild–moderate CAS 3 (Male 1 = 4 inconsistency and dysprosody NR; Male 2 and Female = 3)
McNeill, Gillon, and Dodd (2009a)  Multiple baseline SCED IIb 12 (4;2–7;6, 3 females, 9 males, previous SLP NR) Mild–moderate to severe CAS (no other diagnoses reported) 3 (dysprosody NR)
McNeill, Gillon, and Dodd (2009b)  Multiple baseline SCED IIb 2 (identical twins also in McNeill et al., 2009a) CAS (small interstitial deletion on chromosome 10 (deletion at 10q21.2–22.1) 3 (dysprosody NR)
(4;5, male, moderate–severe)
McNeill, Gillon, and Dodd (2010)  Quasi-experimental group (following SCED) IIb Same participants as McNeill et al. (2009a)  Mild–moderate to severe CAS (no other diagnoses reported) 3 (dysprosody NR)
Rate control therapy Rosenthal (1994)  ABAB single case design (with alternating treatments) IIb 4 (10–14 years, 3 males, 1 female, all had previous SLP) CAS (severity not stated) 4 (dysprosody and inconsistency NR)
MIT Krauss and Galloway (1982)  ABAA single case design IIb 2 (6 and 5 years, male, had previous SLP) CAS (severity not stated) 4 (dysprosody and inconsistency NR)
Partners in augmentative communication training (PACT) Culp (1989)  ABA single case design IIb 1 (8 years, female, 5 years previous SLP) Severe CAS+ 2 (comorbid CAS)
(intellectual disability, Hx tube insertion, congenital heart defect)
Rapid Syllable Transition Treatment (ReST) Ballard, Robin, McCabe, and McDonald (2010)  Multiple baseline across behaviors and participants design IIb 3 (7;8–10;10, 2 males, 1 female, 1–5 years previous SLP) Mild or mild–moderate CAS 1
Voice output devices Bornman, Alant, and Meiring (2001)  ABA single case design IIb 1 (6;6, male, 2.50 years previous SLP) CAS+ (anoxia causing slight left hemiplegia, grand mal fits) 5
Note. Please see the online supplemental materials, Supplemental Table 3, for the 19 Level III articles. SLP = speech-language pathology; CAS+ = comorbid childhood apraxia of speech; GDD = global developmental delay; NR = not reported; VCFS = velocardiofacial syndrome; VPI = velopharyngeal incompetence; LD = language delay/disorder; A = baseline/withdrawal phase; B = treatment/intervention phase; SSD = speech sound disorder; Hx = history of; NDP = Nuffield Dyspraxia Programme; OME = otitis media with effusion/glue ear; CHARGE syndrome = coloboma, heart disease, atresia of the choanae, retarded growth and mental development, genital anomalies, and ear malformations and hearing loss; CLP = cleft lip and palate.
Note. Please see the online supplemental materials, Supplemental Table 3, for the 19 Level III articles. SLP = speech-language pathology; CAS+ = comorbid childhood apraxia of speech; GDD = global developmental delay; NR = not reported; VCFS = velocardiofacial syndrome; VPI = velopharyngeal incompetence; LD = language delay/disorder; A = baseline/withdrawal phase; B = treatment/intervention phase; SSD = speech sound disorder; Hx = history of; NDP = Nuffield Dyspraxia Programme; OME = otitis media with effusion/glue ear; CHARGE syndrome = coloboma, heart disease, atresia of the choanae, retarded growth and mental development, genital anomalies, and ear malformations and hearing loss; CLP = cleft lip and palate.×
Table 2. Research design, level of evidence, participant description, and diagnosis analysis of the 23 Level IIb (SCED) articles.
Research design, level of evidence, participant description, and diagnosis analysis of the 23 Level IIb (SCED) articles.×
Intervention name/approach Published articles Research design Level of evidence Participant description Diagnosis Diagnostic confidence rating
Aided AAC modeling Binger and Light (2007)  Multiple baseline across 3 participants SCED IIb 2/5 (4;2 [years;months] and 4;4, male, had previous SLP) Severe CAS+ (GDD) 4 (dysprosody and sequencing NR)
Binger, Kent-Walsh, Berens, Del Campo, and Rivera (2008)  Multiple baseline across probes SCED IIb 1/3 (3;4, female, previous SLP NR) Severe CAS+ (suspected VCFS with profound VPI) 4 (dysprosody and inconsistency NR)
Binger, Maguire-Marshall, and Kent-Walsh (2011)  Multiple baseline across 3 participants SCED IIb 1/3 (6 years, female, previous SLP NR) Severe CAS+ (receptive and expressive LD) 5
Articulation with facilitative vowel contexts Stokes and Griffiths (2010)  ABA single case design IIb 1 (7 years, male, 1 year previous SLP) Mild SSD (Hx of CAS) 4 (dysprosody and nconsistency NR)
Combined intraoral stimulation, Electropalatography (EPG) with NDP Lundeborg and McAllister (2007)  ABABABABA single case design IIb 1 (5;1, female, 1.50 years previous SLP) Severe CAS 3 (dysprosody NR)
Combined melodic intonation therapy (MIT) and touch cue method (TCM) Martikainen and Korpilahti (2011)  Multiple baseline across participants SCED IIb 1 (4;7, female, 1 year previous SLP) Severe CAS 1
Combined stimulability (STP) and modified core vocabulary (mCVT) Iuzzini and Forrest (2010)  Multiple baseline SCED IIb 4 (3;7–6;10, 2 males, 2 females, previous SLP for 3/4) Severe CAS 4 (dysprosody and sequencing NR)
Computer-based Harris, Doyle, and Haaf (1996)  Multiple baseline across discourse contexts SCED IIb 1 (5 years, male, approximately 3 years previous SLP) Severe CAS+ (Hx OME, receptive and expressive LD) 3 (dysprosody NR)
Integral Stimulation/Dynamic Temporal and Tactile Cueing (DTTC) Strand and Debertine (2000)  Multiple baseline SCED IIb 1 (5 years, female, 4 years previous SLP) Severe CAS (Hx of VPI) 1
Strand, Stoeckel, and Baas (2006)  Multiple baseline SCED IIb 4 (5;5–6;1, all male, 2–4 years previous SLP) Severe CAS+ 4 (for all cases; dysprosody and inconsistency NR, clearly comorbid)
(2 with mild spastic and/or ataxic dysarthria, 1 with mild intellectual disability, and 1 with OME)
Baas, Strand, Elmer, and Barbaresi (2008)  Multiple baseline SCED IIb 1 (12;8, male, 10 years previous SLP) Severe CAS+ (CHARGE syndrome intellectual disability) 5
Edeal and Gildersleeve-Neumann (2011)  AB—alternating treatments single design (with three stable baselines) IIb 2 (6;2 and 3;4, male, 1–4 years previous SLP) 6;2—severe CAS+ (repaired CLP, severe receptive LD), 1
3;4—severe CAS
Maas and Farinella (2012)  Multiple baseline SCED IIb 4 (5;0–7;9, 2 females, 2 males, previous SLP NR) CAS001—moderate–severe CAS; 3 (by consensus); CAS001 = 1, CAS002 = 3 (dysprosody NR, clearly comorbid), CAS005 = 2 (clearly comorbid), CAS010 = 4 (inconsistency and coarticulation NR, clearly comorbid)
CAS002—severe CAS+ (dysarthria);
CAS005—moderate–severe CAS+ (dysarthria and receptive LD); CAS010—mild-moderate CAS+ (sensory processing, fine and gross motor skill delay, hypotonia, moderate–severe receptive LD)
Maas, Butalla, and Farinella (2012)  Multiple baseline SCED IIb 4 (3 in common with Maas & Farinella, 2012) CAS001; 2 (by consensus); as above and CAS012 = 2 (clearly comorbid)
(5;4–8;4, 2 females, 2 males, previous SLP NR) CAS002;
CAS005—see above;
CAS012—CAS+ (moderate–severe receptive LD, Hx OME)
Integrated Phonological Awareness Intervention (N = 5) Moriarty and Gillon (2006)  Multiple baseline SCED IIb 3 (6;3–6;10, 2 males, 1 female, up to 2 years previous SLP) Male 1—Severe CAS+ (receptive and expressive LD); Male 2—Severe CAS+ (receptive and expressive LD); Female—mild–moderate CAS 3 (Male 1 = 4 inconsistency and dysprosody NR; Male 2 and Female = 3)
McNeill, Gillon, and Dodd (2009a)  Multiple baseline SCED IIb 12 (4;2–7;6, 3 females, 9 males, previous SLP NR) Mild–moderate to severe CAS (no other diagnoses reported) 3 (dysprosody NR)
McNeill, Gillon, and Dodd (2009b)  Multiple baseline SCED IIb 2 (identical twins also in McNeill et al., 2009a) CAS (small interstitial deletion on chromosome 10 (deletion at 10q21.2–22.1) 3 (dysprosody NR)
(4;5, male, moderate–severe)
McNeill, Gillon, and Dodd (2010)  Quasi-experimental group (following SCED) IIb Same participants as McNeill et al. (2009a)  Mild–moderate to severe CAS (no other diagnoses reported) 3 (dysprosody NR)
Rate control therapy Rosenthal (1994)  ABAB single case design (with alternating treatments) IIb 4 (10–14 years, 3 males, 1 female, all had previous SLP) CAS (severity not stated) 4 (dysprosody and inconsistency NR)
MIT Krauss and Galloway (1982)  ABAA single case design IIb 2 (6 and 5 years, male, had previous SLP) CAS (severity not stated) 4 (dysprosody and inconsistency NR)
Partners in augmentative communication training (PACT) Culp (1989)  ABA single case design IIb 1 (8 years, female, 5 years previous SLP) Severe CAS+ 2 (comorbid CAS)
(intellectual disability, Hx tube insertion, congenital heart defect)
Rapid Syllable Transition Treatment (ReST) Ballard, Robin, McCabe, and McDonald (2010)  Multiple baseline across behaviors and participants design IIb 3 (7;8–10;10, 2 males, 1 female, 1–5 years previous SLP) Mild or mild–moderate CAS 1
Voice output devices Bornman, Alant, and Meiring (2001)  ABA single case design IIb 1 (6;6, male, 2.50 years previous SLP) CAS+ (anoxia causing slight left hemiplegia, grand mal fits) 5
Note. Please see the online supplemental materials, Supplemental Table 3, for the 19 Level III articles. SLP = speech-language pathology; CAS+ = comorbid childhood apraxia of speech; GDD = global developmental delay; NR = not reported; VCFS = velocardiofacial syndrome; VPI = velopharyngeal incompetence; LD = language delay/disorder; A = baseline/withdrawal phase; B = treatment/intervention phase; SSD = speech sound disorder; Hx = history of; NDP = Nuffield Dyspraxia Programme; OME = otitis media with effusion/glue ear; CHARGE syndrome = coloboma, heart disease, atresia of the choanae, retarded growth and mental development, genital anomalies, and ear malformations and hearing loss; CLP = cleft lip and palate.
Note. Please see the online supplemental materials, Supplemental Table 3, for the 19 Level III articles. SLP = speech-language pathology; CAS+ = comorbid childhood apraxia of speech; GDD = global developmental delay; NR = not reported; VCFS = velocardiofacial syndrome; VPI = velopharyngeal incompetence; LD = language delay/disorder; A = baseline/withdrawal phase; B = treatment/intervention phase; SSD = speech sound disorder; Hx = history of; NDP = Nuffield Dyspraxia Programme; OME = otitis media with effusion/glue ear; CHARGE syndrome = coloboma, heart disease, atresia of the choanae, retarded growth and mental development, genital anomalies, and ear malformations and hearing loss; CLP = cleft lip and palate.×
×
Within the 19 case series and description articles, 25 participants were reported to have CAS, and eight participants were reported to have comorbid CAS (CAS+). Of the 19 articles, three articles (15.8%) received a Level 1 rating for high confidence in diagnosis, zero articles (0.0%) received a Level 2 rating, five articles (26.3%) received a Level 3 rating, five articles (26.3%) received a Level 4 rating, and six articles (31.5%) received a Level 5 rating for no confidence (see the online supplemental materials, Supplemental Table 2). The 19 Level III articles were not analyzed further because of lack of experimental control.
Aim 2: Treatment Procedures
The first section details the classification of treatments on the basis of their approach. The second section presents results on service delivery models used.
Classification of Treatment Goals and Approaches
Eleven of 23 SCED studies were classified as primarily motor approaches (see Table 3). They included primary measures for accuracy of articulation and/or prosody. Two studies included secondary measures of speech intelligibility or comprehensibility (Strand & Debertine, 2000; Strand, Stoeckel, & Baas, 2006). All utilized articulatory placement and imitation cues as well as multimodal cues (e.g., kinesthetic/touch cues, manipulating speech rate and timing, picture or orthographic stimuli). The majority (90%) made explicit reference to incorporating principles of motor learning (PML; see Maas et al., 2008, for a review).
Table 3. Treatment outcomes for the 23 SCED articles.
Treatment outcomes for the 23 SCED articles.×
Therapy type Therapy approach Treatment across all participants
Maintenance Response generalization (Significant in no. of participants) Stimulus generalization (Significant in no. of participants) Judgment of certainty
Cases with reported Rx effect Measures Statistics used? Attained? Time
Motor with cueing Articulation with facilitative vowel contextsa 1/1 Accuracy (/∫/) Yes—significant effects Yes 2 weeks post 1/1 NR Suggestive
Combined intraoral stimulation and EPG (with NDP)b 1/1 (1) PCC, Yes—significant effects for all measures NR NR NR NR Suggestive
(2) PPC,
(3) PWC,
(4) intelligibility, (5) assessment of visual deviancy
Combined MIT and TCMc 1/1 (1) PVC, Yes—1/5 post-MIT (PVC; however, PCC declined)—3/5 significant post-TCM Varied—PVC maintained. 12 weeks post NR NR Suggestive
(2) PCC, PCC and PMLU only significant after MIT withdrawn. Greater changes after withdrawal.
(3) PMLU,
(4) PWP,
(5) PWC
Integral Stimulation/DTTCd 11/13 Rx accuracy Yes—9/13 moderate–large effect sizes Yes for 5/7 (6 NR) 2–4 weeks post 6/7 (6 NR) NR Preponderant
ReSTe 3/3 Perceptual stress matches Yes—significant effects Yes for 2/3 4 weeks post 3/3 NR Preponderant
Rate Control Therapyf 4/4 Rx accuracy No NR NR NR 0/4 to discourse Suggestive
Linguistic with some motor aspects Combined STP and mCVTg 4/4 (only 3/4 for CSIP) (1) PCC, No NR NR NR NR Suggestive
(2) phones added to inventory, (3) ↓ inconsistency (CSIP),
(4) ↓ inconsistency (ISP)
Integrated Phonological Awareness (PA) Interventionh 11/15 (1) % suppression of process usage, Yes—significant effects Yes—as group of 12 (3 NR) 6 months post 11/15 NR Preponderant
(2) PA accuracy
MIT with traditional therapyi 2/2 (1) Porch Index of Communicative Ability in Children, (2) MLU Yes—significant verbal naming and imitation NR NR NR NR Suggestive
Linguistic with some AAC Aided AAC modeling (with communication board or voice output devices)j 4/4 Rx frequency Yes—moderate–large effect sizes Yes for all 2, 4, and 8 weeks post NR (1) 3/3, Suggestive
(1) multisymbol messages (2) NR
(2) morpheme accuracy ↑ speech and participation, ↓ frustration
Computer-based AACk 1/1 Rx accuracy No NR NR NR NR Suggestive
(1) book reading
(2) discourse
AAC Voice output devices—Macawl 1/1 No. of appropriate responses No Yes 4 weeks post NR Spoke intelligibly after 1 year Suggestive
PACTm 1/1 Communicative effectiveness (frequency of turns) No NR NR NR ↑ participation Suggestive
Note. Rx = medical prescription; PCC = percentage of consonants correct; PPC = percentage of phonemes correct; PWC = percentage of words correct; PVC = percentage of vowels correct; PMLU = phonological mean length of utterance; PWP = proportion of whole-word proximity; CSIP = consonant substitute inconsistency percentage; ISP = inconsistency severity percentage; MLU = mean length of utterance.
Note. Rx = medical prescription; PCC = percentage of consonants correct; PPC = percentage of phonemes correct; PWC = percentage of words correct; PVC = percentage of vowels correct; PMLU = phonological mean length of utterance; PWP = proportion of whole-word proximity; CSIP = consonant substitute inconsistency percentage; ISP = inconsistency severity percentage; MLU = mean length of utterance.×
a Stokes and Griffiths (2010) . b Lundeborg and McAllister (2007) . c Martikainen and Korpilahti (2011) . d Strand and Debertine (2000), Strand et al. (2006), Baas et al. (2008), Edeal and Gildersleeve-Neumann (2011), Maas and Farinella (2012), and Maas et al. (2012) . e Ballard et al. (2010) . f Rosenthal (1994) . g Iuzzini and Forrest (2010) . h Moriarty and Gillon (2006)  and McNeill et al. (2009a, 2009b, 2010) . i Krauss and Galloway (1982) . j Binger and Light (2007)  and Binger et al. (2008, 2011) . k Harris et al. (1996) . l Bornman et al. (2001) . m Culp (1989) . MIT completed in the first block, and TCM completed in the second block.
MIT completed in the first block, and TCM completed in the second block.×
Table 3. Treatment outcomes for the 23 SCED articles.
Treatment outcomes for the 23 SCED articles.×
Therapy type Therapy approach Treatment across all participants
Maintenance Response generalization (Significant in no. of participants) Stimulus generalization (Significant in no. of participants) Judgment of certainty
Cases with reported Rx effect Measures Statistics used? Attained? Time
Motor with cueing Articulation with facilitative vowel contextsa 1/1 Accuracy (/∫/) Yes—significant effects Yes 2 weeks post 1/1 NR Suggestive
Combined intraoral stimulation and EPG (with NDP)b 1/1 (1) PCC, Yes—significant effects for all measures NR NR NR NR Suggestive
(2) PPC,
(3) PWC,
(4) intelligibility, (5) assessment of visual deviancy
Combined MIT and TCMc 1/1 (1) PVC, Yes—1/5 post-MIT (PVC; however, PCC declined)—3/5 significant post-TCM Varied—PVC maintained. 12 weeks post NR NR Suggestive
(2) PCC, PCC and PMLU only significant after MIT withdrawn. Greater changes after withdrawal.
(3) PMLU,
(4) PWP,
(5) PWC
Integral Stimulation/DTTCd 11/13 Rx accuracy Yes—9/13 moderate–large effect sizes Yes for 5/7 (6 NR) 2–4 weeks post 6/7 (6 NR) NR Preponderant
ReSTe 3/3 Perceptual stress matches Yes—significant effects Yes for 2/3 4 weeks post 3/3 NR Preponderant
Rate Control Therapyf 4/4 Rx accuracy No NR NR NR 0/4 to discourse Suggestive
Linguistic with some motor aspects Combined STP and mCVTg 4/4 (only 3/4 for CSIP) (1) PCC, No NR NR NR NR Suggestive
(2) phones added to inventory, (3) ↓ inconsistency (CSIP),
(4) ↓ inconsistency (ISP)
Integrated Phonological Awareness (PA) Interventionh 11/15 (1) % suppression of process usage, Yes—significant effects Yes—as group of 12 (3 NR) 6 months post 11/15 NR Preponderant
(2) PA accuracy
MIT with traditional therapyi 2/2 (1) Porch Index of Communicative Ability in Children, (2) MLU Yes—significant verbal naming and imitation NR NR NR NR Suggestive
Linguistic with some AAC Aided AAC modeling (with communication board or voice output devices)j 4/4 Rx frequency Yes—moderate–large effect sizes Yes for all 2, 4, and 8 weeks post NR (1) 3/3, Suggestive
(1) multisymbol messages (2) NR
(2) morpheme accuracy ↑ speech and participation, ↓ frustration
Computer-based AACk 1/1 Rx accuracy No NR NR NR NR Suggestive
(1) book reading
(2) discourse
AAC Voice output devices—Macawl 1/1 No. of appropriate responses No Yes 4 weeks post NR Spoke intelligibly after 1 year Suggestive
PACTm 1/1 Communicative effectiveness (frequency of turns) No NR NR NR ↑ participation Suggestive
Note. Rx = medical prescription; PCC = percentage of consonants correct; PPC = percentage of phonemes correct; PWC = percentage of words correct; PVC = percentage of vowels correct; PMLU = phonological mean length of utterance; PWP = proportion of whole-word proximity; CSIP = consonant substitute inconsistency percentage; ISP = inconsistency severity percentage; MLU = mean length of utterance.
Note. Rx = medical prescription; PCC = percentage of consonants correct; PPC = percentage of phonemes correct; PWC = percentage of words correct; PVC = percentage of vowels correct; PMLU = phonological mean length of utterance; PWP = proportion of whole-word proximity; CSIP = consonant substitute inconsistency percentage; ISP = inconsistency severity percentage; MLU = mean length of utterance.×
a Stokes and Griffiths (2010) . b Lundeborg and McAllister (2007) . c Martikainen and Korpilahti (2011) . d Strand and Debertine (2000), Strand et al. (2006), Baas et al. (2008), Edeal and Gildersleeve-Neumann (2011), Maas and Farinella (2012), and Maas et al. (2012) . e Ballard et al. (2010) . f Rosenthal (1994) . g Iuzzini and Forrest (2010) . h Moriarty and Gillon (2006)  and McNeill et al. (2009a, 2009b, 2010) . i Krauss and Galloway (1982) . j Binger and Light (2007)  and Binger et al. (2008, 2011) . k Harris et al. (1996) . l Bornman et al. (2001) . m Culp (1989) . MIT completed in the first block, and TCM completed in the second block.
MIT completed in the first block, and TCM completed in the second block.×
×
Ten studies were classified as primarily linguistic approaches. Of these, six studies reported primary measures of speech sound production (phonological processes or stimulability), phonological awareness accuracy, and spoken language utterance length, which also used some motor cueing (Iuzzini & Forrest, 2010; Krauss & Galloway, 1982; McNeill, Gillon, & Dodd, 2009a, 2009b, 2010; Moriarty & Gillon, 2006). The other four studies targeted expressive language skills (e.g., multisymbol messages or elaborated phrase structures) using AAC systems in children with previously established AAC use (Binger, Kent-Walsh, Berens, Del Campo, & Rivera, 2008; Binger & Light, 2007; Binger, Maguire-Marshall, & Kent-Walsh, 2011; Harris, Doyle, & Haaf, 1996).
Two studies were classified as AAC, measuring communicative effectiveness in children with severe comorbid CAS (CAS+), by introducing AAC systems (Bornman, Alant, & Meiring, 2001; Culp, 1989). These children had reportedly shown slow or minimal progress in speech production attempts and/or used AAC to alleviate frustration and behavioral problems due to communication failure.
A total of 13 treatment approaches were identified across the 23 studies; six were solely or primarily motor, five were linguistic, and two were AAC (see Table 3). Seven of these 13 approaches represented combined approaches. Of these, two combined two motor treatments (Lundeborg & McAllister, 2007; Rosenthal, 1994), and another two combined linguistic treatments (Iuzzini & Forrest, 2010; McNeill et al., 2009a), not affecting their classification. Another two combined a linguistic treatment (melodic intonation therapy [MIT]) with a motor treatment, either touch cue method (TCM; Martikainen & Korpilahti, 2011) or traditional articulation therapy (Krauss & Galloway, 1982). The first was classified as a motor approach because of the goals and PML incorporated; the second was classified as a linguistic approach, as MIT was the primary experimental approach, and linguistic outcomes were primarily sought and reported. Finally, for one motor treatment, the participant continued regular AAC therapy during the research (Edeal & Gildersleeve-Neumann, 2011).
Structure of Treatment Delivery
All 23 treatments were delivered individually, with 22 delivered in a clinic and one delivered at the participant's home (Lundeborg & McAllister, 2007). Caregiver and child training sessions were utilized in the two AAC studies within a consultative-collaboration service delivery model (Bornman et al., 2001; Culp, 1989). Inclusion of parent training and home practice protocols or activities was more prevalent in AAC-based treatments and was used in six of 23 articles.
For motor treatments reporting dose frequency, the median was three times a week, with a maximum of once a day and minimum of twice a week. Sessions were between 20 and 60 min long. Most linguistic and AAC approaches provided treatment two to three times a week for between 15- and 60-min sessions. A small number gave intensive daily, short-term training. Dose in terms of treatment trials completed within sessions was adequately described in five of 23 articles or three of 13 approaches and ranged from 60 to 120 trials for motor approaches and from 10 to 30 trials for linguistic and AAC approaches (Ballard, Robin, McCabe, & McDonald, 2010; Binger et al., 2008; Binger & Light, 2007; Binger et al., 2011; Stokes & Griffiths, 2010). Further details of the treatment procedure analyses for each study and approach are provided in the online supplemental materials, Supplemental Table 3.
Aim 3: Treatment Outcomes
Analyses of treatment, maintenance, and generalization outcomes for the 23 SCED articles are reported in Table 3. All studies used baseline phases, and 91% incorporated untrained control items intended to demonstrate some experimental control.
Treatment and Maintenance Data
All articles reported treatment effects for the majority of the participants, despite a range of goals and measures being used. Statistical comparison of at least one key outcome was provided for 16 of 23 studies.
Of the 23 participants given motor-based treatment, 21 were reported to demonstrate positive treatment effects, and a statistical analysis of effects was reported for 17 (see Table 3). Not all participants showed significant changes in all measures assessed. The majority of measures consisted of percentage of accuracy on treated items or percentage of consonant, vowel, phonemes, or words correct. Three studies demonstrated improvement for treated prosodic accuracy: Ballard et al. (2010)  for three of three participants using the Rapid Syllable Transition Treatment (ReST) and Maas, Butalla, and Farinella (2012)  and Maas and Farinella (2012)  for three of four participants following Dynamic Temporal and Tactile Cueing (DTTC; in any PML condition). The combined MIT/TCM treatment showed significantly improved percentage of vowels correct; however, it significantly reduced percentage of consonants correct for the participant immediately post the first block of MIT. The greatest gains were noted after withdrawal of treatment. Despite the authors suggesting this to be due to the treatments given, this equally may be due to maturation or improvement after withdrawal of treatment providing unclear evidence to the effect of these treatments.
Six studies of linguistic-based treatment reported a treatment effect for speech measures for 17 of 21 participants, with 16 of 21 participants supported by statistical comparison (Iuzzini & Forrest, 2010; Krauss & Galloway, 1982; McNeill et al., 2009a, 2009b, 2010; Moriarty & Gillon, 2006). With Integrated Phonological Awareness Intervention, 11 of 15 participants were reported to reduce phonological processes and to improve phonological awareness skills. Another four articles reported that five of five participants increased use of multisymbol messages (phrases or morphemes) with linguistic-based treatment utilizing AAC (Binger et al., 2008; Binger & Light, 2007; Binger et al., 2011; Harris et al., 1996).
Finally, AAC treatment studies focusing on communicative effectiveness reported treatment effects for two of two participants, with no statistical analyses conducted (Bornman et al., 2001; Culp, 1989). The children reportedly increased appropriate responses and frequency of turns in conversation.
Generalization
Seven articles considered response generalization, and another five considered stimulus generalization. No article measured both response and stimulus generalization.
Response generalization. All treatments measuring generalization used statistical analysis. For motor-based treatments, significant improvement in articulation accuracy for untrained responses was noted for one participant after facilitative vowel treatment (Stokes & Griffiths, 2010) and for four of seven participants across any behavior/condition in three studies applying Integral Stimulation/DTTC (Edeal & Gildersleeve-Neumann, 2011; Maas et al., 2012; Maas & Farinella, 2012). Significant generalization was reported for three of three participants for lexical stress accuracy in untrained three syllable pseudowords and for one of three participants in untrained real word production for ReST treatment (Ballard et al., 2010).
Only one linguistic-based approach, the Integrated Phonological Awareness Intervention, reported response generalization. The same 11 of 15 children who demonstrated treatment gains also showed significant improvement in speech intelligibility, mean length of utterance, and phonological awareness skills (phoneme segregation, manipulation, nonword reading, reading accuracy, and letter–sound correspondences; McNeill et al., 2009a, 2009b, 2010; Moriarty & Gillon, 2006).
Stimulus generalization. Only five articles (22%) reported stimulus generalization, with four of these utilizing AAC treatments. Three participants, who increased grammatical constituents in treatment, also generalized use of symbol combinations across different scenarios or discourse types (Binger et al., 2008; Binger & Light, 2007). Anecdotal reports, predominately from caregivers, suggested improved expressive language skills or communication across settings, reduced frustration due to AAC device use (Binger & Light, 2007; Culp, 1989), and transition to reliance on speech (Bornman et al., 2001). There was one reported instance of poor stimulus generalization; rate control therapy showed minimal generalization from the treated reading task to untreated conversation (Rosenthal, 1994).
Aim 4: Certainty of Evidence
The level of certainty that the effects of each treatment were true (Smith, 1981) is reported in Table 3. No treatment approaches met the criteria for conclusive evidence. Three treatment approaches, two motor (Integral Stimulation/DTTC, ReST) and one linguistic (Integrated Phonological Awareness Intervention), met the criteria for preponderant evidence (replicated evidence across participants with promising treatment, maintenance, and generalization data). The remaining approaches qualified as suggestive evidence. These included studies with questionable effects (e.g., combined MIT/TCM treatment), as there was not a specific category for these within Smith's (1981)  framework. Two studies with suggestive evidence approached preponderant evidence: Aided AAC modeling met all the criteria except for confidence in CAS diagnosis, and the facilitative vowel contexts treatment reported only one case with low confidence in CAS diagnosis.
The overall treatment effect size for each of the three approaches with preponderant evidence was determined using IRD (Parker et al., 2009; see Table 4). Integral Stimulation/DTTC demonstrated a moderate effect size for articulation and/or prosodic accuracy (IRD = 0.60) for seven participants ranging in age from 3;4 (years;months) to 8;4 with mild–moderate to severe CAS or CAS+. Integrated Phonological Awareness Intervention also demonstrated moderate effect sizes for percentage of phonemes correct (IRD = 0.51) for 15 participants ranging in age from 4;2 to 7;6 with mild–moderate to severe CAS. Finally, ReST demonstrated a large effect size for prosodic accuracy (IRD = 0.78) for three participants ranging in age from 7;8 to 10;10 with mild to mild–moderate CAS.
Table 4. Omnibus improvement rate differences (IRDs) for preponderant evidence—treatment effects.
Omnibus improvement rate differences (IRDs) for preponderant evidence—treatment effects.×
Treatment type Treatment approach Article No. of cases Confidence in CAS Dxa Omnibus IRD 95% CI Interpretation of effect
Motor Integral Stimulation/DTTCb Strand and Debertine (2000)  1 1 1.00 [0.97, 1.00] Very large
Edeal and Gildersleeve-Neumann (2011)  2 1 0.98 [0.88, 1.00] Very large
Maas and Farinella (2012)  4c 3 0.18 [0.03, 0.33] Small or questionable
Maas et al. (2012)  4c 2 0.22 [0.08, 0.36] Small or questionable
Overall 0.60 [0.53, 0.67] Moderate
ReST Ballard et al. (2010)  3 1 0.78 [0.54, 1.00] Large (prosody—PVI duration)
Linguistic Integrated Phonological Awareness Intervention Moriarty and Gillon (2006)  3 3 1.00 [0.89, 1.00] Very large
McNeill et al. (2009a)  12 3 0.10 [−0.06, 0.24] Small or questionable
Overall 0.51 [0.39, 0.58] Moderate
Note. CI = confidence interval; PVI = pairwise variability index (acoustic measure).
Note. CI = confidence interval; PVI = pairwise variability index (acoustic measure).×
a 1 = highest.
1 = highest.×
b Baas et al. (2008)  and Strand et al. (2006)  were excluded from IRD because of diagnostic confidence ratings of 4 and 5.
Baas et al. (2008)  and Strand et al. (2006)  were excluded from IRD because of diagnostic confidence ratings of 4 and 5.×
c Three participants in common across two studies.
Three participants in common across two studies.×
Table 4. Omnibus improvement rate differences (IRDs) for preponderant evidence—treatment effects.
Omnibus improvement rate differences (IRDs) for preponderant evidence—treatment effects.×
Treatment type Treatment approach Article No. of cases Confidence in CAS Dxa Omnibus IRD 95% CI Interpretation of effect
Motor Integral Stimulation/DTTCb Strand and Debertine (2000)  1 1 1.00 [0.97, 1.00] Very large
Edeal and Gildersleeve-Neumann (2011)  2 1 0.98 [0.88, 1.00] Very large
Maas and Farinella (2012)  4c 3 0.18 [0.03, 0.33] Small or questionable
Maas et al. (2012)  4c 2 0.22 [0.08, 0.36] Small or questionable
Overall 0.60 [0.53, 0.67] Moderate
ReST Ballard et al. (2010)  3 1 0.78 [0.54, 1.00] Large (prosody—PVI duration)
Linguistic Integrated Phonological Awareness Intervention Moriarty and Gillon (2006)  3 3 1.00 [0.89, 1.00] Very large
McNeill et al. (2009a)  12 3 0.10 [−0.06, 0.24] Small or questionable
Overall 0.51 [0.39, 0.58] Moderate
Note. CI = confidence interval; PVI = pairwise variability index (acoustic measure).
Note. CI = confidence interval; PVI = pairwise variability index (acoustic measure).×
a 1 = highest.
1 = highest.×
b Baas et al. (2008)  and Strand et al. (2006)  were excluded from IRD because of diagnostic confidence ratings of 4 and 5.
Baas et al. (2008)  and Strand et al. (2006)  were excluded from IRD because of diagnostic confidence ratings of 4 and 5.×
c Three participants in common across two studies.
Three participants in common across two studies.×
×
Generalization effects varied according to the treatment and measures used, and thus a separate effect size was calculated per measure/condition (see Table 5). The motor treatments of Integral Stimulation/DTTC and ReST showed predominantly small effect sizes, with some moderate-to-large effects (ranging from IRD = −0.20 to IRD = 0.84). The Integrated Phonological Awareness Intervention showed a large effect size for percentage of phonemes correct (IRD = 0.80).
Table 5. Omnibus IRDs for preponderant evidence—generalization.
Omnibus IRDs for preponderant evidence—generalization.×
Therapy type Therapy approach Article No. of cases Confidence in CAS Dx (1 = highest) Generalization to untrained itemsa IRD 95% CI Interpretation of effect
Motor Integral Stimulation/DTTCb Strand and Debertine (2000)  1 1 NR NR NA NA
Edeal and Gildersleeve-Neumann (2011)  2 1 MFF sounds 0.05 [10.47, 0.57] Small or questionable
HFF sounds 0.60 [0.18, 1.00] Moderate
Maas and Farinella (2012)  4c 3 Blocked practice items 0.04 [−0.16, 0.24] Small or questionable
Random practice items 0.20 [0.01, 0.39] Small or questionable
Maas et al. (2012)  4c 2 100% feedback items −0.15 [−0.13, 0.43] Small or questionable
60% feedback items 0.03 [−0.14, 0.20] Small or questionable
ReST Ballard et al. (2010)  3 1 Less complex pseudowords (PVI duration) 0.84 [0.62, 1.00] Large
Real words (PVI duration) 0.13 [−0.21, 0.47] Small or questionable
Linguistic Integrated Phonological Awareness Intervention Moriarty and Gillon (2006)  3 3 NR NR NA NA
McNeill et al. (2009a)  12 3 Untrained PPC 0.80 [0.64, 0.88] Large
Note. NA = not applicable; MFF = moderate frequency feedback; HFF = high frequency feedback.
Note. NA = not applicable; MFF = moderate frequency feedback; HFF = high frequency feedback.×
a Generalization items were individualized for each participant.
Generalization items were individualized for each participant.×
b Baas et al. (2008)  and Strand et al. (2006)  were excluded from IRD because of diagnostic confidence ratings of 4 and 5.
Baas et al. (2008)  and Strand et al. (2006)  were excluded from IRD because of diagnostic confidence ratings of 4 and 5.×
c Three participants in common across two studies.
Three participants in common across two studies.×
Table 5. Omnibus IRDs for preponderant evidence—generalization.
Omnibus IRDs for preponderant evidence—generalization.×
Therapy type Therapy approach Article No. of cases Confidence in CAS Dx (1 = highest) Generalization to untrained itemsa IRD 95% CI Interpretation of effect
Motor Integral Stimulation/DTTCb Strand and Debertine (2000)  1 1 NR NR NA NA
Edeal and Gildersleeve-Neumann (2011)  2 1 MFF sounds 0.05 [10.47, 0.57] Small or questionable
HFF sounds 0.60 [0.18, 1.00] Moderate
Maas and Farinella (2012)  4c 3 Blocked practice items 0.04 [−0.16, 0.24] Small or questionable
Random practice items 0.20 [0.01, 0.39] Small or questionable
Maas et al. (2012)  4c 2 100% feedback items −0.15 [−0.13, 0.43] Small or questionable
60% feedback items 0.03 [−0.14, 0.20] Small or questionable
ReST Ballard et al. (2010)  3 1 Less complex pseudowords (PVI duration) 0.84 [0.62, 1.00] Large
Real words (PVI duration) 0.13 [−0.21, 0.47] Small or questionable
Linguistic Integrated Phonological Awareness Intervention Moriarty and Gillon (2006)  3 3 NR NR NA NA
McNeill et al. (2009a)  12 3 Untrained PPC 0.80 [0.64, 0.88] Large
Note. NA = not applicable; MFF = moderate frequency feedback; HFF = high frequency feedback.
Note. NA = not applicable; MFF = moderate frequency feedback; HFF = high frequency feedback.×
a Generalization items were individualized for each participant.
Generalization items were individualized for each participant.×
b Baas et al. (2008)  and Strand et al. (2006)  were excluded from IRD because of diagnostic confidence ratings of 4 and 5.
Baas et al. (2008)  and Strand et al. (2006)  were excluded from IRD because of diagnostic confidence ratings of 4 and 5.×
c Three participants in common across two studies.
Three participants in common across two studies.×
×
Discussion
The aim of this study was to conduct an in-depth and systematic review of treatment efficacy studies for children with CAS. Unlike previous reviews, we considered within-subject experimental designs with Level IIb evidence to identify promising treatment approaches for further study and for cautious application in clinical settings. Twenty-three studies qualified for in-depth review, and three treatment approaches, tested in seven studies, reached the level of preponderant evidence with promising evidence of efficacy across several participants diagnosed with CAS (confidence rating of 1–3).
Study Quality
The vast majority of studies examining treatment for CAS are single case studies, with an increasing trend toward more rigorous experimental designs over time. This trend may be a consequence of critical narrative reviews in the late 1980s and 1990s (e.g., Hall et al., 1993; McCabe et al., 1998; Pannbacker, 1988) and greater awareness of research design and evidence-based practice (ASHA, 2004). The body of research reflects Phase I and Phase II studies (Robey, 2004) designed to test the feasibility and early efficacy of treatments. At this stage, no Phase III RCT or NRCT reports are available to contribute to conclusive evidence (Smith, 1981). Therefore, no conclusions as to which treatments are more efficacious than others for CAS are currently possible (ASHA, 2007; Morgan & Vogel, 2009; Pannbacker, 1988). This review identified preponderant evidence and well-designed, quasi-experimental studies that can guide clinical decisions and that are suitable to pursue in more substantive comparative efficacy studies.
Certainty of Evidence
Two motor treatments (Integral Stimulation/DTTC and ReST) and one linguistic treatment (Integrated Phonological Awareness Intervention) demonstrated preponderant evidence (Smith, 1981) with positive treatment and generalization effects across several children. Only Integral Stimulation/DTTC is supported currently by studies across independent research groups (Baas, Strand, Elmer, & Barbaresi, 2008; Edeal & Gildersleeve-Neumann, 2011; Maas et al., 2012; Maas & Farinella, 2012; Strand & Debertine, 2000; Strand et al., 2006), although such replication was not directly analyzed here. SCED ratings in the future could be elaborated beyond replication for external validity and application of the same protocol in direct replication studies (Tate et al., 2013) to also include independence of research groups. Currently, no direct replication studies exist for CAS treatment.
The remaining articles were classified as suggestive evidence. With future well-controlled investigation, some of these treatments, as well as others excluded from this review, will likely emerge as promising options for CAS. Additionally, an extra level of certainty should be considered for future reviews flagging studies with questionable effects (i.e., those that did not demonstrate clear treatment effects).
Confidence in CAS Diagnosis
A critical component of any treatment study is a clear definition of the study participants to convince readers that the appropriate population was targeted. When the 2007 consensus-based diagnostic features (ASHA, 2007) were applied, only 16.6% achieved a rating of high confidence. However, most of the studies reviewed were published prior to 2007 and were using common descriptors for their time, now considered by many to be nondiscriminative (e.g., ASHA, 2007; McCabe et al., 1998). The most commonly overlooked CAS characteristic across studies was dysprosody, which was not considered a core feature of CAS in many checklists prior to 2007. As prosody (e.g., lexical or phrasal stress) is primarily conveyed on vowels, we counted mention of vowel errors in participants as possible evidence of dysprosody to accommodate older articles. Despite the chance that dysprosody would be overestimated because of this decision (as only a subset of vowel errors or distortions would be indicative of stress errors), only 50% of the articles (21 of 42) reported vowel errors. Furthermore, the high rate of comorbidity in CAS (41% in this sample) complicates diagnosis and could partially account for lower confidence ratings.
Experimental Control
Experimental control is essential to ensure that treatment effects are attributable to the intervention approach provided and are an essential element to calculating effect sizes for single-subject designs (Olswang & Bain, 1994). Only experimental designs with some experimental control were included in the treatment outcome analysis. Experimental control was best demonstrated when SCEDs reported change in at least one condition beyond baseline levels after withdrawal of treatment and when control data were used to estimate improvement due to maturation (Byiers et al., 2012; Olswang & Bain, 1994; Perdices & Tate, 2009). Not all of the studies analyzed here demonstrated clear experimental control and treatment effects on the basis of these conditions. In future research, CAS SCEDs would ideally use more than two phases (i.e., beyond just baseline and treatment but also withdrawal and other treatment phases), including at least three data points per phase (including baselines) and replication across cases (Tate et al., 2013).
Within this review, 22% (five of 23) of the articles at Level IIb of evidence reported some changes in untreated speech behaviors, which were hypothesized to be unrelated to the treated behaviors. This phenomenon reflects a loss of experimental control and may undermine the claim of positive treatment effects. However, it may also reflect the underspecification of theories of speech motor control, in that there is limited evidence to guide how and why speech behaviors are related motorically (Folkins & Bleile, 1990). This issue has been more fully discussed in studies of treatment of acquired apraxia of speech (Ballard, 2001; Ballard, Maas, & Robin, 2007). These unexpected generalization outcomes may provide interesting directions for exploring relationships between different speech skills and for guiding the selection of generalization and control stimuli in future treatment trials.
Treatment Approaches
The reviewed treatments for CAS can be categorized as targeting motor or linguistic skills or using AAC to provide a primary means of communication. The approaches used can also be viewed in light of the International Classification of Functioning, Disability, and Health (ICF; World Health Organization, 2002). Motor and linguistic approaches were primarily directed at the impairment (body functions/structure) level of the ICF (McLeod & McCormack, 2007), commonly addressing articulation, prosody, phonological awareness, or expressive language skills. AAC approaches were instead directed at the activity/participation levels of the ICF, facilitating communicative effectiveness with a greater emphasis on consultation, training, and home practice. The literature suggests that the primary concern in CAS is developing intelligible speech, either through addressing articulatory and prosodic accuracy or through improving phonology, although concentration on AAC and expressive language may be required.
The majority of SCEDs intentionally combined treatments, a trend that appears to be increasing. This may be due to the hypothesized links between speech motor and linguistic difficulties in children with CAS (Souza, Payão, & Costa, 2009). However, the studies using combined approaches had participants without comorbid CAS and often combined approaches within the same therapy type (e.g., two motor treatments). The theoretical motivation for combining such treatments is unclear, and no comparisons of single versus combined treatments for children with clear diagnoses of CAS are yet available.
Treatment Outcomes
It is well accepted that the strongest evidence for a treatment efficacy is demonstration of skill maintenance beyond the treatment period and generalization of treatment effects to related behaviors and/or communication contexts (e.g., McReynolds & Kearns, 1983; Schmidt & Lee, 2011). Such effects constitute instrumental clinical change (Olswang & Bain, 1994, 2013). Few of the 23 studies evaluated reported maintenance of treatment or generalization effects. As such, the robustness of most reported treatment effects over time is not known.
The six approaches that demonstrated maintenance and response or stimulus generalization were the three approaches with preponderant evidence (Integral Stimulation/DTTC, ReST, and Integrated Phonological Awareness Intervention) and the aided AAC modeling and facilitative vowel context interventions. Degree of generalization varied, seemingly influenced by specific stimuli chosen, incorporation of PML, dosage, frequency and intensity of sessions, potential critical thresholds for skill mastery, and participant characteristics. Notably, only those participants demonstrating strong gains for treated behaviors tended to maintain or generalize skills (e.g., Maas & Farinella, 2012; McNeill et al., 2009a). The exception to this was the phonological treatment within the Integrated Phonological Awareness Intervention, which showed large generalization effects despite demonstrating moderate treatment effects. This is an expected outcome in interventions that focus on learning linguistic rules that can be rapidly generalized across a range of contexts (Gierut, 1998; Gierut & Hulse, 2010) versus learning new motor skills. There are at least two possible explanations for why children with probable CAS, a motor speech disorder, responded to a phonological treatment. First, phonological therapy involves production of speech targets and so provides practice in planning, programming, and executing the movements for these targets. Second, the participants had a number of phonological processes, and perhaps their concomitant phonological disorders were a primary concern for treatment at this time. These findings warrant thoughtful comparison of specific participant characteristics, each intervention's theoretical framework, the stimuli and activities used during intervention, and stimuli used to assess generalization of skill to determine whether there is in fact any benefit in one approach over the other.
Likewise, stimulus generalization provides important information about how skills treated in therapy generalize to other contexts or situations for improvement in everyday communication. Only rate control therapy (Rosenthal, 1994) and AAC approaches considered such generalization. Such measures should be employed as we move toward Phase III and Phase IV studies to demonstrate real change in communication skills in children with CAS.
It is important to note that, despite most children in the studies showing positive effects in treatment, all children required additional therapy to work on other communication goals after treatment blocks spanning between nine and 195 sessions. This demonstrates that children with CAS often require ongoing therapy, spanning many goals and needs.
Further investigation is warranted to explore interactions between participant variables and the degree of treatment outcome to help tailor treatments, particularly for those who did not demonstrate treatment effects. For example, Integral Simulation/DTTC was initially designed for children with severe CAS using functional core vocabulary stimuli (Strand & Skinder, 1999). Whereas studies addressing severe CAS have reported positive treatment effects across multiple participants, those addressing mild-to-moderate CAS and specific sound, prosody, and/or word structure goals have had small omnibus effect sizes (Maas et al., 2012; Maas & Farinella, 2012).
Similarly, it is yet to be determined whether AAC approaches can promote speech gains over and above speech-based interventions (as described in Bornman et al., 2001). The current literature suggests that when a child experienced frustration over low intelligibility or comprehensibility, AAC approaches may increase communicative success as well as stimulate development of language skills that cannot be practiced through speaking.
Structure of Treatment Delivery
Intensive treatment delivery in impairment-based intervention appears crucial for obtaining positive treatment outcomes. These treatments provided therapy at least 2–3 times a week, with sessions of up to 60 min. The dose of treatment, defined as the “number of properly administrated teaching episodes during a single intervention session” (Warren et al., 2007, p. 71), should probably also be high (Edeal & Gildersleeve-Neumann, 2011). This review suggests that at least 60 trials per session represents a “high” dose. Williams (2012)  suggested that, with phonological therapy for speech sound disorder, ≥50 trials per session over ≥30 sessions is effective, although dose and intensity need to increase as impairment severity increases. Further research is indicated to allow reliable estimates of the overall amount of therapy needed, dose, and intensity for CAS, considering age and severity.
SCED studies in this review all delivered treatment in individual sessions, and 40% utilized home practice to increase dose and intensity. The high intensity that is indicated would clearly require significant resources. Thus, determining effective treatments with engaging home practice activities should maximize maintenance and generalization of skills.
Implications
Despite a continued need for well-designed RCTs, NRCTs, and additional SCED studies, existing evidence is available to guide clinical practice in the treatment of CAS. Comparing treatments is a future priority, considering the range of treatments that are available. The treatments best suited to inclusion in an RCT or NRCT are those that have demonstrated maintenance and generalization effects. Further research is needed for valid and reliable differential diagnosis of CAS and for understanding which client groups would benefit from which type of treatment.
In terms of clinical practice, currently two motor treatments (Integral Stimulation/DTTC and ReST) and one linguistic treatment (Integrated Phonological Awareness Intervention) are best suited to interim clinical use, with sessions at least twice a week and dose above 60 trials per session. DTTC appears to work better for clients with more severe CAS, Integrated Phonological Awareness Intervention appears to work better for children 4–7 years of age with mild to severe CAS, and ReST appears to work better for children 7–10 years of age with mild-to-moderate CAS.
Limitations
Because of the developing nature of this literature, this systematic review utilized some narrative review methodology to ensure greater coverage of SCED designs that differed considerably (Collins & Fauser, 2004). Potential bias was reduced through the use of systematic review principles.
We considered only peer-reviewed published reports in English. We did not control for publication bias, as we excluded evidence that had not undergone journal-level peer review. This means that evidence from conference presentations or dissertations was excluded, thus excluding other approaches with potential suggestive evidence, such as Prompts for Restructuring Oral Muscular Phonetic Targets (Dale & Hayden, 2011; now see Dale & Hayden, 2013) or the Nuffield Dyspraxia Programme (Belton, 2006). As in all reviews, there is a risk that studies with negative treatment outcomes are underrepresented because of the difficulty publishing such studies, potentially risking overestimation of treatment effects.
Our IRD analysis examined preliminary effect sizes but did not use moderator variables because of the small number of articles (n = 7) and participants (n = 26). Here, we provide some preliminary observations about which treatments appear useful for different age and severity levels. As additional studies are published, it is recommended that such moderator variables be evaluated more fully.
It is important to note the IRD is calculated and interpreted differently to other effect sizes. For example, the recent DTTC studies (Maas et al., 2012; Maas & Farinella, 2012) used Beeson and Robey's (2006)  effect size method and found large effect sizes for some participants and conditions and found no effects for others. As the majority of articles did not report means and standard deviations, such effect size calculations were not possible across all preponderant articles. The IRDs reported here differ from those reported in Maas et al. (2012)  and Maas and Farinella (2012)  in two ways. First, in our calculation of IRD, only nonoverlapping data between baseline/withdrawal and treatment phases were considered indicative of improvement. Second, the IRDs here were averaged across participants within studies; thus, greater variability across participants conservatively reduced the magnitude of the omnibus IRD.
Other aspects that could be investigated were beyond the scope of the current study. This includes SCED methodological quality as per reported guidelines (e.g., Tate et al., 2013; see Wendt & Miller, 2012, for a review) and analysis of motor learning principles utilized in each treatment (e.g., Bislick, Weir, Spencer, Kendall, & Yorkston, 2012). We did not evaluate the theoretical stance of each treatment approach, which might have revealed further information as to why some treatments generated stronger effects than others.
Conclusion
This review identified 23 SCED articles reporting 13 treatment approaches classified as primarily motor, linguistic, or AAC. Three treatments were judged to have preponderant evidence to support their efficacy, indicating that the reported effects were “probably true”: Integral Stimulation/DTTC, ReST, and Integrated Phonological Awareness Intervention. These treatments had moderate-to-large treatment effects and small-to-large generalization effects, making them strong candidates for Phase III research, comparison in RCTs, and interim clinical use. Larger scale rigorous RCTs and NRCTs are critically needed to compare treatments with larger sample sizes to potentially inform a greater number of clients with CAS (Morgan & Vogel, 2009). Such efforts will serve to generate conclusive evidence through well-controlled experimental designs, including measures of maintenance and generalization of treatment effects and manipulation of treatment intensity and other motor learning principles. This work will be facilitated by parallel work toward a reliable diagnostic system and exploration of participant variables that influence treatment response.
Acknowledgments
This research was supported by the Douglas and Lola Douglas Scholarship on Child and Adolescent Health, the Speech Pathology Australia Nadia Verrall Memorial Research Grant and Postgraduate Research Award, and the University of Sydney James Kentley Memorial Scholarship and Postgraduate Research Support Scheme awarded to the first author. This research was also supported by an Australian Research Council Future Fellowship awarded to the third author. We thank Catherine Mason and Donna Thomas for assistance coding the data and completing reliability.
References

References marked with an asterisk indicate studies included in the improvement rate difference analysis.

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Figure 1.

Flow diagram of study selection (adapted from Preferred Reporting Items for Systematic Reviews and Meta-Analyses [PRISMA]; Moher et al., 2009). CAS = childhood apraxia of speech; Ax = assessment; Dx = diagnosis; RCT = randomized controlled trial; NRCT = nonrandomized controlled trial; SCED = single-case experimental design; AAC = augmentative and alternative communication.

 Flow diagram of study selection (adapted from Preferred Reporting Items for Systematic Reviews and Meta-Analyses [PRISMA]; Moher et al., 2009). CAS = childhood apraxia of speech; Ax = assessment; Dx = diagnosis; RCT = randomized controlled trial; NRCT = nonrandomized controlled trial; SCED = single-case experimental design; AAC = augmentative and alternative communication.
Figure 1.

Flow diagram of study selection (adapted from Preferred Reporting Items for Systematic Reviews and Meta-Analyses [PRISMA]; Moher et al., 2009). CAS = childhood apraxia of speech; Ax = assessment; Dx = diagnosis; RCT = randomized controlled trial; NRCT = nonrandomized controlled trial; SCED = single-case experimental design; AAC = augmentative and alternative communication.

×
Table 1. Five-point rating scale of confidence in diagnosis of CAS (adapted from the Academy of Neurologic Communication Disorders and Sciences guidelines; Wambaugh et al., 2006).
Five-point rating scale of confidence in diagnosis of CAS (adapted from the Academy of Neurologic Communication Disorders and Sciences guidelines; Wambaugh et al., 2006).×
Level Primary characteristics Nondiscriminative characteristics Comorbidity
Level 1 All the primary characteristics were described as follows: CAS was the primary diagnosis described. Any characteristics that were attributable to other disorders may have been described but were not used to diagnose CAS. CAS without another comorbid disorder was reported (excluding expressive language delay).
 • Inconsistency and
 • Lengthened and disrupted coarticulatory transitions between sounds and syllables and
 • Inappropriate prosody.
Level 2 All the primary characteristics were described as follows: CAS was the primary diagnosis described. Other characteristics attributable to other disorders (e.g., dysarthria) were described and may have been used to diagnose CAS. This includes the following:
 • Inconsistency and  • CAS without another comorbid disorder (excluding expressive language delay) or
 • Lengthened and disrupted coarticulatory transitions between sounds and syllables and  • Clear cases of comorbid CAS, in which CAS was the primary diagnosis.
 • Inappropriate prosody.
Level 3 Two of the three primary characteristics were described: CAS was described. Other characteristics that were attributable to other disorders (e.g., dysarthria) were described and may have been used to diagnose CAS. This includes the following:
 • Inconsistency and/or  • CAS without another comorbid disorder or
 • Lengthened and disrupted coarticulatory transitions between sounds and syllables and/or  • Clear cases of comorbid CAS, in which CAS was the primary diagnosis or
 • Inappropriate prosody.  • Cases of CAS in which another comorbid disorder had the same severity (e.g., language delay, dysarthria).
Level 4 Only one of the three primary characteristics was reported, or incomplete/inadequate description of the primary characteristics of CAS was provided. Other characteristics that were attributable to other disorders may have been described, and it is unclear whether these were used to diagnose CAS. Unclear whether CAS was the primary diagnosis.
Level 5 Diagnosis of CAS was reported or implied, but no primary characteristics were described. Unclear whether CAS diagnosis was likely and/or whether CAS was the primary diagnosis. Other comorbid disorders may be present.
Table 1. Five-point rating scale of confidence in diagnosis of CAS (adapted from the Academy of Neurologic Communication Disorders and Sciences guidelines; Wambaugh et al., 2006).
Five-point rating scale of confidence in diagnosis of CAS (adapted from the Academy of Neurologic Communication Disorders and Sciences guidelines; Wambaugh et al., 2006).×
Level Primary characteristics Nondiscriminative characteristics Comorbidity
Level 1 All the primary characteristics were described as follows: CAS was the primary diagnosis described. Any characteristics that were attributable to other disorders may have been described but were not used to diagnose CAS. CAS without another comorbid disorder was reported (excluding expressive language delay).
 • Inconsistency and
 • Lengthened and disrupted coarticulatory transitions between sounds and syllables and
 • Inappropriate prosody.
Level 2 All the primary characteristics were described as follows: CAS was the primary diagnosis described. Other characteristics attributable to other disorders (e.g., dysarthria) were described and may have been used to diagnose CAS. This includes the following:
 • Inconsistency and  • CAS without another comorbid disorder (excluding expressive language delay) or
 • Lengthened and disrupted coarticulatory transitions between sounds and syllables and  • Clear cases of comorbid CAS, in which CAS was the primary diagnosis.
 • Inappropriate prosody.
Level 3 Two of the three primary characteristics were described: CAS was described. Other characteristics that were attributable to other disorders (e.g., dysarthria) were described and may have been used to diagnose CAS. This includes the following:
 • Inconsistency and/or  • CAS without another comorbid disorder or
 • Lengthened and disrupted coarticulatory transitions between sounds and syllables and/or  • Clear cases of comorbid CAS, in which CAS was the primary diagnosis or
 • Inappropriate prosody.  • Cases of CAS in which another comorbid disorder had the same severity (e.g., language delay, dysarthria).
Level 4 Only one of the three primary characteristics was reported, or incomplete/inadequate description of the primary characteristics of CAS was provided. Other characteristics that were attributable to other disorders may have been described, and it is unclear whether these were used to diagnose CAS. Unclear whether CAS was the primary diagnosis.
Level 5 Diagnosis of CAS was reported or implied, but no primary characteristics were described. Unclear whether CAS diagnosis was likely and/or whether CAS was the primary diagnosis. Other comorbid disorders may be present.
×
Table 2. Research design, level of evidence, participant description, and diagnosis analysis of the 23 Level IIb (SCED) articles.
Research design, level of evidence, participant description, and diagnosis analysis of the 23 Level IIb (SCED) articles.×
Intervention name/approach Published articles Research design Level of evidence Participant description Diagnosis Diagnostic confidence rating
Aided AAC modeling Binger and Light (2007)  Multiple baseline across 3 participants SCED IIb 2/5 (4;2 [years;months] and 4;4, male, had previous SLP) Severe CAS+ (GDD) 4 (dysprosody and sequencing NR)
Binger, Kent-Walsh, Berens, Del Campo, and Rivera (2008)  Multiple baseline across probes SCED IIb 1/3 (3;4, female, previous SLP NR) Severe CAS+ (suspected VCFS with profound VPI) 4 (dysprosody and inconsistency NR)
Binger, Maguire-Marshall, and Kent-Walsh (2011)  Multiple baseline across 3 participants SCED IIb 1/3 (6 years, female, previous SLP NR) Severe CAS+ (receptive and expressive LD) 5
Articulation with facilitative vowel contexts Stokes and Griffiths (2010)  ABA single case design IIb 1 (7 years, male, 1 year previous SLP) Mild SSD (Hx of CAS) 4 (dysprosody and nconsistency NR)
Combined intraoral stimulation, Electropalatography (EPG) with NDP Lundeborg and McAllister (2007)  ABABABABA single case design IIb 1 (5;1, female, 1.50 years previous SLP) Severe CAS 3 (dysprosody NR)
Combined melodic intonation therapy (MIT) and touch cue method (TCM) Martikainen and Korpilahti (2011)  Multiple baseline across participants SCED IIb 1 (4;7, female, 1 year previous SLP) Severe CAS 1
Combined stimulability (STP) and modified core vocabulary (mCVT) Iuzzini and Forrest (2010)  Multiple baseline SCED IIb 4 (3;7–6;10, 2 males, 2 females, previous SLP for 3/4) Severe CAS 4 (dysprosody and sequencing NR)
Computer-based Harris, Doyle, and Haaf (1996)  Multiple baseline across discourse contexts SCED IIb 1 (5 years, male, approximately 3 years previous SLP) Severe CAS+ (Hx OME, receptive and expressive LD) 3 (dysprosody NR)
Integral Stimulation/Dynamic Temporal and Tactile Cueing (DTTC) Strand and Debertine (2000)  Multiple baseline SCED IIb 1 (5 years, female, 4 years previous SLP) Severe CAS (Hx of VPI) 1
Strand, Stoeckel, and Baas (2006)  Multiple baseline SCED IIb 4 (5;5–6;1, all male, 2–4 years previous SLP) Severe CAS+ 4 (for all cases; dysprosody and inconsistency NR, clearly comorbid)
(2 with mild spastic and/or ataxic dysarthria, 1 with mild intellectual disability, and 1 with OME)
Baas, Strand, Elmer, and Barbaresi (2008)  Multiple baseline SCED IIb 1 (12;8, male, 10 years previous SLP) Severe CAS+ (CHARGE syndrome intellectual disability) 5
Edeal and Gildersleeve-Neumann (2011)  AB—alternating treatments single design (with three stable baselines) IIb 2 (6;2 and 3;4, male, 1–4 years previous SLP) 6;2—severe CAS+ (repaired CLP, severe receptive LD), 1
3;4—severe CAS
Maas and Farinella (2012)  Multiple baseline SCED IIb 4 (5;0–7;9, 2 females, 2 males, previous SLP NR) CAS001—moderate–severe CAS; 3 (by consensus); CAS001 = 1, CAS002 = 3 (dysprosody NR, clearly comorbid), CAS005 = 2 (clearly comorbid), CAS010 = 4 (inconsistency and coarticulation NR, clearly comorbid)
CAS002—severe CAS+ (dysarthria);
CAS005—moderate–severe CAS+ (dysarthria and receptive LD); CAS010—mild-moderate CAS+ (sensory processing, fine and gross motor skill delay, hypotonia, moderate–severe receptive LD)
Maas, Butalla, and Farinella (2012)  Multiple baseline SCED IIb 4 (3 in common with Maas & Farinella, 2012) CAS001; 2 (by consensus); as above and CAS012 = 2 (clearly comorbid)
(5;4–8;4, 2 females, 2 males, previous SLP NR) CAS002;
CAS005—see above;
CAS012—CAS+ (moderate–severe receptive LD, Hx OME)
Integrated Phonological Awareness Intervention (N = 5) Moriarty and Gillon (2006)  Multiple baseline SCED IIb 3 (6;3–6;10, 2 males, 1 female, up to 2 years previous SLP) Male 1—Severe CAS+ (receptive and expressive LD); Male 2—Severe CAS+ (receptive and expressive LD); Female—mild–moderate CAS 3 (Male 1 = 4 inconsistency and dysprosody NR; Male 2 and Female = 3)
McNeill, Gillon, and Dodd (2009a)  Multiple baseline SCED IIb 12 (4;2–7;6, 3 females, 9 males, previous SLP NR) Mild–moderate to severe CAS (no other diagnoses reported) 3 (dysprosody NR)
McNeill, Gillon, and Dodd (2009b)  Multiple baseline SCED IIb 2 (identical twins also in McNeill et al., 2009a) CAS (small interstitial deletion on chromosome 10 (deletion at 10q21.2–22.1) 3 (dysprosody NR)
(4;5, male, moderate–severe)
McNeill, Gillon, and Dodd (2010)  Quasi-experimental group (following SCED) IIb Same participants as McNeill et al. (2009a)  Mild–moderate to severe CAS (no other diagnoses reported) 3 (dysprosody NR)
Rate control therapy Rosenthal (1994)  ABAB single case design (with alternating treatments) IIb 4 (10–14 years, 3 males, 1 female, all had previous SLP) CAS (severity not stated) 4 (dysprosody and inconsistency NR)
MIT Krauss and Galloway (1982)  ABAA single case design IIb 2 (6 and 5 years, male, had previous SLP) CAS (severity not stated) 4 (dysprosody and inconsistency NR)
Partners in augmentative communication training (PACT) Culp (1989)  ABA single case design IIb 1 (8 years, female, 5 years previous SLP) Severe CAS+ 2 (comorbid CAS)
(intellectual disability, Hx tube insertion, congenital heart defect)
Rapid Syllable Transition Treatment (ReST) Ballard, Robin, McCabe, and McDonald (2010)  Multiple baseline across behaviors and participants design IIb 3 (7;8–10;10, 2 males, 1 female, 1–5 years previous SLP) Mild or mild–moderate CAS 1
Voice output devices Bornman, Alant, and Meiring (2001)  ABA single case design IIb 1 (6;6, male, 2.50 years previous SLP) CAS+ (anoxia causing slight left hemiplegia, grand mal fits) 5
Note. Please see the online supplemental materials, Supplemental Table 3, for the 19 Level III articles. SLP = speech-language pathology; CAS+ = comorbid childhood apraxia of speech; GDD = global developmental delay; NR = not reported; VCFS = velocardiofacial syndrome; VPI = velopharyngeal incompetence; LD = language delay/disorder; A = baseline/withdrawal phase; B = treatment/intervention phase; SSD = speech sound disorder; Hx = history of; NDP = Nuffield Dyspraxia Programme; OME = otitis media with effusion/glue ear; CHARGE syndrome = coloboma, heart disease, atresia of the choanae, retarded growth and mental development, genital anomalies, and ear malformations and hearing loss; CLP = cleft lip and palate.
Note. Please see the online supplemental materials, Supplemental Table 3, for the 19 Level III articles. SLP = speech-language pathology; CAS+ = comorbid childhood apraxia of speech; GDD = global developmental delay; NR = not reported; VCFS = velocardiofacial syndrome; VPI = velopharyngeal incompetence; LD = language delay/disorder; A = baseline/withdrawal phase; B = treatment/intervention phase; SSD = speech sound disorder; Hx = history of; NDP = Nuffield Dyspraxia Programme; OME = otitis media with effusion/glue ear; CHARGE syndrome = coloboma, heart disease, atresia of the choanae, retarded growth and mental development, genital anomalies, and ear malformations and hearing loss; CLP = cleft lip and palate.×
Table 2. Research design, level of evidence, participant description, and diagnosis analysis of the 23 Level IIb (SCED) articles.
Research design, level of evidence, participant description, and diagnosis analysis of the 23 Level IIb (SCED) articles.×
Intervention name/approach Published articles Research design Level of evidence Participant description Diagnosis Diagnostic confidence rating
Aided AAC modeling Binger and Light (2007)  Multiple baseline across 3 participants SCED IIb 2/5 (4;2 [years;months] and 4;4, male, had previous SLP) Severe CAS+ (GDD) 4 (dysprosody and sequencing NR)
Binger, Kent-Walsh, Berens, Del Campo, and Rivera (2008)  Multiple baseline across probes SCED IIb 1/3 (3;4, female, previous SLP NR) Severe CAS+ (suspected VCFS with profound VPI) 4 (dysprosody and inconsistency NR)
Binger, Maguire-Marshall, and Kent-Walsh (2011)  Multiple baseline across 3 participants SCED IIb 1/3 (6 years, female, previous SLP NR) Severe CAS+ (receptive and expressive LD) 5
Articulation with facilitative vowel contexts Stokes and Griffiths (2010)  ABA single case design IIb 1 (7 years, male, 1 year previous SLP) Mild SSD (Hx of CAS) 4 (dysprosody and nconsistency NR)
Combined intraoral stimulation, Electropalatography (EPG) with NDP Lundeborg and McAllister (2007)  ABABABABA single case design IIb 1 (5;1, female, 1.50 years previous SLP) Severe CAS 3 (dysprosody NR)
Combined melodic intonation therapy (MIT) and touch cue method (TCM) Martikainen and Korpilahti (2011)  Multiple baseline across participants SCED IIb 1 (4;7, female, 1 year previous SLP) Severe CAS 1
Combined stimulability (STP) and modified core vocabulary (mCVT) Iuzzini and Forrest (2010)  Multiple baseline SCED IIb 4 (3;7–6;10, 2 males, 2 females, previous SLP for 3/4) Severe CAS 4 (dysprosody and sequencing NR)
Computer-based Harris, Doyle, and Haaf (1996)  Multiple baseline across discourse contexts SCED IIb 1 (5 years, male, approximately 3 years previous SLP) Severe CAS+ (Hx OME, receptive and expressive LD) 3 (dysprosody NR)
Integral Stimulation/Dynamic Temporal and Tactile Cueing (DTTC) Strand and Debertine (2000)  Multiple baseline SCED IIb 1 (5 years, female, 4 years previous SLP) Severe CAS (Hx of VPI) 1
Strand, Stoeckel, and Baas (2006)  Multiple baseline SCED IIb 4 (5;5–6;1, all male, 2–4 years previous SLP) Severe CAS+ 4 (for all cases; dysprosody and inconsistency NR, clearly comorbid)
(2 with mild spastic and/or ataxic dysarthria, 1 with mild intellectual disability, and 1 with OME)
Baas, Strand, Elmer, and Barbaresi (2008)  Multiple baseline SCED IIb 1 (12;8, male, 10 years previous SLP) Severe CAS+ (CHARGE syndrome intellectual disability) 5
Edeal and Gildersleeve-Neumann (2011)  AB—alternating treatments single design (with three stable baselines) IIb 2 (6;2 and 3;4, male, 1–4 years previous SLP) 6;2—severe CAS+ (repaired CLP, severe receptive LD), 1
3;4—severe CAS
Maas and Farinella (2012)  Multiple baseline SCED IIb 4 (5;0–7;9, 2 females, 2 males, previous SLP NR) CAS001—moderate–severe CAS; 3 (by consensus); CAS001 = 1, CAS002 = 3 (dysprosody NR, clearly comorbid), CAS005 = 2 (clearly comorbid), CAS010 = 4 (inconsistency and coarticulation NR, clearly comorbid)
CAS002—severe CAS+ (dysarthria);
CAS005—moderate–severe CAS+ (dysarthria and receptive LD); CAS010—mild-moderate CAS+ (sensory processing, fine and gross motor skill delay, hypotonia, moderate–severe receptive LD)
Maas, Butalla, and Farinella (2012)  Multiple baseline SCED IIb 4 (3 in common with Maas & Farinella, 2012) CAS001; 2 (by consensus); as above and CAS012 = 2 (clearly comorbid)
(5;4–8;4, 2 females, 2 males, previous SLP NR) CAS002;
CAS005—see above;
CAS012—CAS+ (moderate–severe receptive LD, Hx OME)
Integrated Phonological Awareness Intervention (N = 5) Moriarty and Gillon (2006)  Multiple baseline SCED IIb 3 (6;3–6;10, 2 males, 1 female, up to 2 years previous SLP) Male 1—Severe CAS+ (receptive and expressive LD); Male 2—Severe CAS+ (receptive and expressive LD); Female—mild–moderate CAS 3 (Male 1 = 4 inconsistency and dysprosody NR; Male 2 and Female = 3)
McNeill, Gillon, and Dodd (2009a)  Multiple baseline SCED IIb 12 (4;2–7;6, 3 females, 9 males, previous SLP NR) Mild–moderate to severe CAS (no other diagnoses reported) 3 (dysprosody NR)
McNeill, Gillon, and Dodd (2009b)  Multiple baseline SCED IIb 2 (identical twins also in McNeill et al., 2009a) CAS (small interstitial deletion on chromosome 10 (deletion at 10q21.2–22.1) 3 (dysprosody NR)
(4;5, male, moderate–severe)
McNeill, Gillon, and Dodd (2010)  Quasi-experimental group (following SCED) IIb Same participants as McNeill et al. (2009a)  Mild–moderate to severe CAS (no other diagnoses reported) 3 (dysprosody NR)
Rate control therapy Rosenthal (1994)  ABAB single case design (with alternating treatments) IIb 4 (10–14 years, 3 males, 1 female, all had previous SLP) CAS (severity not stated) 4 (dysprosody and inconsistency NR)
MIT Krauss and Galloway (1982)  ABAA single case design IIb 2 (6 and 5 years, male, had previous SLP) CAS (severity not stated) 4 (dysprosody and inconsistency NR)
Partners in augmentative communication training (PACT) Culp (1989)  ABA single case design IIb 1 (8 years, female, 5 years previous SLP) Severe CAS+ 2 (comorbid CAS)
(intellectual disability, Hx tube insertion, congenital heart defect)
Rapid Syllable Transition Treatment (ReST) Ballard, Robin, McCabe, and McDonald (2010)  Multiple baseline across behaviors and participants design IIb 3 (7;8–10;10, 2 males, 1 female, 1–5 years previous SLP) Mild or mild–moderate CAS 1
Voice output devices Bornman, Alant, and Meiring (2001)  ABA single case design IIb 1 (6;6, male, 2.50 years previous SLP) CAS+ (anoxia causing slight left hemiplegia, grand mal fits) 5
Note. Please see the online supplemental materials, Supplemental Table 3, for the 19 Level III articles. SLP = speech-language pathology; CAS+ = comorbid childhood apraxia of speech; GDD = global developmental delay; NR = not reported; VCFS = velocardiofacial syndrome; VPI = velopharyngeal incompetence; LD = language delay/disorder; A = baseline/withdrawal phase; B = treatment/intervention phase; SSD = speech sound disorder; Hx = history of; NDP = Nuffield Dyspraxia Programme; OME = otitis media with effusion/glue ear; CHARGE syndrome = coloboma, heart disease, atresia of the choanae, retarded growth and mental development, genital anomalies, and ear malformations and hearing loss; CLP = cleft lip and palate.
Note. Please see the online supplemental materials, Supplemental Table 3, for the 19 Level III articles. SLP = speech-language pathology; CAS+ = comorbid childhood apraxia of speech; GDD = global developmental delay; NR = not reported; VCFS = velocardiofacial syndrome; VPI = velopharyngeal incompetence; LD = language delay/disorder; A = baseline/withdrawal phase; B = treatment/intervention phase; SSD = speech sound disorder; Hx = history of; NDP = Nuffield Dyspraxia Programme; OME = otitis media with effusion/glue ear; CHARGE syndrome = coloboma, heart disease, atresia of the choanae, retarded growth and mental development, genital anomalies, and ear malformations and hearing loss; CLP = cleft lip and palate.×
×
Table 3. Treatment outcomes for the 23 SCED articles.
Treatment outcomes for the 23 SCED articles.×
Therapy type Therapy approach Treatment across all participants
Maintenance Response generalization (Significant in no. of participants) Stimulus generalization (Significant in no. of participants) Judgment of certainty
Cases with reported Rx effect Measures Statistics used? Attained? Time
Motor with cueing Articulation with facilitative vowel contextsa 1/1 Accuracy (/∫/) Yes—significant effects Yes 2 weeks post 1/1 NR Suggestive
Combined intraoral stimulation and EPG (with NDP)b 1/1 (1) PCC, Yes—significant effects for all measures NR NR NR NR Suggestive
(2) PPC,
(3) PWC,
(4) intelligibility, (5) assessment of visual deviancy
Combined MIT and TCMc 1/1 (1) PVC, Yes—1/5 post-MIT (PVC; however, PCC declined)—3/5 significant post-TCM Varied—PVC maintained. 12 weeks post NR NR Suggestive
(2) PCC, PCC and PMLU only significant after MIT withdrawn. Greater changes after withdrawal.
(3) PMLU,
(4) PWP,
(5) PWC
Integral Stimulation/DTTCd 11/13 Rx accuracy Yes—9/13 moderate–large effect sizes Yes for 5/7 (6 NR) 2–4 weeks post 6/7 (6 NR) NR Preponderant
ReSTe 3/3 Perceptual stress matches Yes—significant effects Yes for 2/3 4 weeks post 3/3 NR Preponderant
Rate Control Therapyf 4/4 Rx accuracy No NR NR NR 0/4 to discourse Suggestive
Linguistic with some motor aspects Combined STP and mCVTg 4/4 (only 3/4 for CSIP) (1) PCC, No NR NR NR NR Suggestive
(2) phones added to inventory, (3) ↓ inconsistency (CSIP),
(4) ↓ inconsistency (ISP)
Integrated Phonological Awareness (PA) Interventionh 11/15 (1) % suppression of process usage, Yes—significant effects Yes—as group of 12 (3 NR) 6 months post 11/15 NR Preponderant
(2) PA accuracy
MIT with traditional therapyi 2/2 (1) Porch Index of Communicative Ability in Children, (2) MLU Yes—significant verbal naming and imitation NR NR NR NR Suggestive
Linguistic with some AAC Aided AAC modeling (with communication board or voice output devices)j 4/4 Rx frequency Yes—moderate–large effect sizes Yes for all 2, 4, and 8 weeks post NR (1) 3/3, Suggestive
(1) multisymbol messages (2) NR
(2) morpheme accuracy ↑ speech and participation, ↓ frustration
Computer-based AACk 1/1 Rx accuracy No NR NR NR NR Suggestive
(1) book reading
(2) discourse
AAC Voice output devices—Macawl 1/1 No. of appropriate responses No Yes 4 weeks post NR Spoke intelligibly after 1 year Suggestive
PACTm 1/1 Communicative effectiveness (frequency of turns) No NR NR NR ↑ participation Suggestive
Note. Rx = medical prescription; PCC = percentage of consonants correct; PPC = percentage of phonemes correct; PWC = percentage of words correct; PVC = percentage of vowels correct; PMLU = phonological mean length of utterance; PWP = proportion of whole-word proximity; CSIP = consonant substitute inconsistency percentage; ISP = inconsistency severity percentage; MLU = mean length of utterance.
Note. Rx = medical prescription; PCC = percentage of consonants correct; PPC = percentage of phonemes correct; PWC = percentage of words correct; PVC = percentage of vowels correct; PMLU = phonological mean length of utterance; PWP = proportion of whole-word proximity; CSIP = consonant substitute inconsistency percentage; ISP = inconsistency severity percentage; MLU = mean length of utterance.×
a Stokes and Griffiths (2010) . b Lundeborg and McAllister (2007) . c Martikainen and Korpilahti (2011) . d Strand and Debertine (2000), Strand et al. (2006), Baas et al. (2008), Edeal and Gildersleeve-Neumann (2011), Maas and Farinella (2012), and Maas et al. (2012) . e Ballard et al. (2010) . f Rosenthal (1994) . g Iuzzini and Forrest (2010) . h Moriarty and Gillon (2006)  and McNeill et al. (2009a, 2009b, 2010) . i Krauss and Galloway (1982) . j Binger and Light (2007)  and Binger et al. (2008, 2011) . k Harris et al. (1996) . l Bornman et al. (2001) . m Culp (1989) . MIT completed in the first block, and TCM completed in the second block.
MIT completed in the first block, and TCM completed in the second block.×
Table 3. Treatment outcomes for the 23 SCED articles.
Treatment outcomes for the 23 SCED articles.×
Therapy type Therapy approach Treatment across all participants
Maintenance Response generalization (Significant in no. of participants) Stimulus generalization (Significant in no. of participants) Judgment of certainty
Cases with reported Rx effect Measures Statistics used? Attained? Time
Motor with cueing Articulation with facilitative vowel contextsa 1/1 Accuracy (/∫/) Yes—significant effects Yes 2 weeks post 1/1 NR Suggestive
Combined intraoral stimulation and EPG (with NDP)b 1/1 (1) PCC, Yes—significant effects for all measures NR NR NR NR Suggestive
(2) PPC,
(3) PWC,
(4) intelligibility, (5) assessment of visual deviancy
Combined MIT and TCMc 1/1 (1) PVC, Yes—1/5 post-MIT (PVC; however, PCC declined)—3/5 significant post-TCM Varied—PVC maintained. 12 weeks post NR NR Suggestive
(2) PCC, PCC and PMLU only significant after MIT withdrawn. Greater changes after withdrawal.
(3) PMLU,
(4) PWP,
(5) PWC
Integral Stimulation/DTTCd 11/13 Rx accuracy Yes—9/13 moderate–large effect sizes Yes for 5/7 (6 NR) 2–4 weeks post 6/7 (6 NR) NR Preponderant
ReSTe 3/3 Perceptual stress matches Yes—significant effects Yes for 2/3 4 weeks post 3/3 NR Preponderant
Rate Control Therapyf 4/4 Rx accuracy No NR NR NR 0/4 to discourse Suggestive
Linguistic with some motor aspects Combined STP and mCVTg 4/4 (only 3/4 for CSIP) (1) PCC, No NR NR NR NR Suggestive
(2) phones added to inventory, (3) ↓ inconsistency (CSIP),
(4) ↓ inconsistency (ISP)
Integrated Phonological Awareness (PA) Interventionh 11/15 (1) % suppression of process usage, Yes—significant effects Yes—as group of 12 (3 NR) 6 months post 11/15 NR Preponderant
(2) PA accuracy
MIT with traditional therapyi 2/2 (1) Porch Index of Communicative Ability in Children, (2) MLU Yes—significant verbal naming and imitation NR NR NR NR Suggestive
Linguistic with some AAC Aided AAC modeling (with communication board or voice output devices)j 4/4 Rx frequency Yes—moderate–large effect sizes Yes for all 2, 4, and 8 weeks post NR (1) 3/3, Suggestive
(1) multisymbol messages (2) NR
(2) morpheme accuracy ↑ speech and participation, ↓ frustration
Computer-based AACk 1/1 Rx accuracy No NR NR NR NR Suggestive
(1) book reading
(2) discourse
AAC Voice output devices—Macawl 1/1 No. of appropriate responses No Yes 4 weeks post NR Spoke intelligibly after 1 year Suggestive
PACTm 1/1 Communicative effectiveness (frequency of turns) No NR NR NR ↑ participation Suggestive
Note. Rx = medical prescription; PCC = percentage of consonants correct; PPC = percentage of phonemes correct; PWC = percentage of words correct; PVC = percentage of vowels correct; PMLU = phonological mean length of utterance; PWP = proportion of whole-word proximity; CSIP = consonant substitute inconsistency percentage; ISP = inconsistency severity percentage; MLU = mean length of utterance.
Note. Rx = medical prescription; PCC = percentage of consonants correct; PPC = percentage of phonemes correct; PWC = percentage of words correct; PVC = percentage of vowels correct; PMLU = phonological mean length of utterance; PWP = proportion of whole-word proximity; CSIP = consonant substitute inconsistency percentage; ISP = inconsistency severity percentage; MLU = mean length of utterance.×
a Stokes and Griffiths (2010) . b Lundeborg and McAllister (2007) . c Martikainen and Korpilahti (2011) . d Strand and Debertine (2000), Strand et al. (2006), Baas et al. (2008), Edeal and Gildersleeve-Neumann (2011), Maas and Farinella (2012), and Maas et al. (2012) . e Ballard et al. (2010) . f Rosenthal (1994) . g Iuzzini and Forrest (2010) . h Moriarty and Gillon (2006)  and McNeill et al. (2009a, 2009b, 2010) . i Krauss and Galloway (1982) . j Binger and Light (2007)  and Binger et al. (2008, 2011) . k Harris et al. (1996) . l Bornman et al. (2001) . m Culp (1989) . MIT completed in the first block, and TCM completed in the second block.
MIT completed in the first block, and TCM completed in the second block.×
×
Table 4. Omnibus improvement rate differences (IRDs) for preponderant evidence—treatment effects.
Omnibus improvement rate differences (IRDs) for preponderant evidence—treatment effects.×
Treatment type Treatment approach Article No. of cases Confidence in CAS Dxa Omnibus IRD 95% CI Interpretation of effect
Motor Integral Stimulation/DTTCb Strand and Debertine (2000)  1 1 1.00 [0.97, 1.00] Very large
Edeal and Gildersleeve-Neumann (2011)  2 1 0.98 [0.88, 1.00] Very large
Maas and Farinella (2012)  4c 3 0.18 [0.03, 0.33] Small or questionable
Maas et al. (2012)  4c 2 0.22 [0.08, 0.36] Small or questionable
Overall 0.60 [0.53, 0.67] Moderate
ReST Ballard et al. (2010)  3 1 0.78 [0.54, 1.00] Large (prosody—PVI duration)
Linguistic Integrated Phonological Awareness Intervention Moriarty and Gillon (2006)  3 3 1.00 [0.89, 1.00] Very large
McNeill et al. (2009a)  12 3 0.10 [−0.06, 0.24] Small or questionable
Overall 0.51 [0.39, 0.58] Moderate
Note. CI = confidence interval; PVI = pairwise variability index (acoustic measure).
Note. CI = confidence interval; PVI = pairwise variability index (acoustic measure).×
a 1 = highest.
1 = highest.×
b Baas et al. (2008)  and Strand et al. (2006)  were excluded from IRD because of diagnostic confidence ratings of 4 and 5.
Baas et al. (2008)  and Strand et al. (2006)  were excluded from IRD because of diagnostic confidence ratings of 4 and 5.×
c Three participants in common across two studies.
Three participants in common across two studies.×
Table 4. Omnibus improvement rate differences (IRDs) for preponderant evidence—treatment effects.
Omnibus improvement rate differences (IRDs) for preponderant evidence—treatment effects.×
Treatment type Treatment approach Article No. of cases Confidence in CAS Dxa Omnibus IRD 95% CI Interpretation of effect
Motor Integral Stimulation/DTTCb Strand and Debertine (2000)  1 1 1.00 [0.97, 1.00] Very large
Edeal and Gildersleeve-Neumann (2011)  2 1 0.98 [0.88, 1.00] Very large
Maas and Farinella (2012)  4c 3 0.18 [0.03, 0.33] Small or questionable
Maas et al. (2012)  4c 2 0.22 [0.08, 0.36] Small or questionable
Overall 0.60 [0.53, 0.67] Moderate
ReST Ballard et al. (2010)  3 1 0.78 [0.54, 1.00] Large (prosody—PVI duration)
Linguistic Integrated Phonological Awareness Intervention Moriarty and Gillon (2006)  3 3 1.00 [0.89, 1.00] Very large
McNeill et al. (2009a)  12 3 0.10 [−0.06, 0.24] Small or questionable
Overall 0.51 [0.39, 0.58] Moderate
Note. CI = confidence interval; PVI = pairwise variability index (acoustic measure).
Note. CI = confidence interval; PVI = pairwise variability index (acoustic measure).×
a 1 = highest.
1 = highest.×
b Baas et al. (2008)  and Strand et al. (2006)  were excluded from IRD because of diagnostic confidence ratings of 4 and 5.
Baas et al. (2008)  and Strand et al. (2006)  were excluded from IRD because of diagnostic confidence ratings of 4 and 5.×
c Three participants in common across two studies.
Three participants in common across two studies.×
×
Table 5. Omnibus IRDs for preponderant evidence—generalization.
Omnibus IRDs for preponderant evidence—generalization.×
Therapy type Therapy approach Article No. of cases Confidence in CAS Dx (1 = highest) Generalization to untrained itemsa IRD 95% CI Interpretation of effect
Motor Integral Stimulation/DTTCb Strand and Debertine (2000)  1 1 NR NR NA NA
Edeal and Gildersleeve-Neumann (2011)  2 1 MFF sounds 0.05 [10.47, 0.57] Small or questionable
HFF sounds 0.60 [0.18, 1.00] Moderate
Maas and Farinella (2012)  4c 3 Blocked practice items 0.04 [−0.16, 0.24] Small or questionable
Random practice items 0.20 [0.01, 0.39] Small or questionable
Maas et al. (2012)  4c 2 100% feedback items −0.15 [−0.13, 0.43] Small or questionable
60% feedback items 0.03 [−0.14, 0.20] Small or questionable
ReST Ballard et al. (2010)  3 1 Less complex pseudowords (PVI duration) 0.84 [0.62, 1.00] Large
Real words (PVI duration) 0.13 [−0.21, 0.47] Small or questionable
Linguistic Integrated Phonological Awareness Intervention Moriarty and Gillon (2006)  3 3 NR NR NA NA
McNeill et al. (2009a)  12 3 Untrained PPC 0.80 [0.64, 0.88] Large
Note. NA = not applicable; MFF = moderate frequency feedback; HFF = high frequency feedback.
Note. NA = not applicable; MFF = moderate frequency feedback; HFF = high frequency feedback.×
a Generalization items were individualized for each participant.
Generalization items were individualized for each participant.×
b Baas et al. (2008)  and Strand et al. (2006)  were excluded from IRD because of diagnostic confidence ratings of 4 and 5.
Baas et al. (2008)  and Strand et al. (2006)  were excluded from IRD because of diagnostic confidence ratings of 4 and 5.×
c Three participants in common across two studies.
Three participants in common across two studies.×
Table 5. Omnibus IRDs for preponderant evidence—generalization.
Omnibus IRDs for preponderant evidence—generalization.×
Therapy type Therapy approach Article No. of cases Confidence in CAS Dx (1 = highest) Generalization to untrained itemsa IRD 95% CI Interpretation of effect
Motor Integral Stimulation/DTTCb Strand and Debertine (2000)  1 1 NR NR NA NA
Edeal and Gildersleeve-Neumann (2011)  2 1 MFF sounds 0.05 [10.47, 0.57] Small or questionable
HFF sounds 0.60 [0.18, 1.00] Moderate
Maas and Farinella (2012)  4c 3 Blocked practice items 0.04 [−0.16, 0.24] Small or questionable
Random practice items 0.20 [0.01, 0.39] Small or questionable
Maas et al. (2012)  4c 2 100% feedback items −0.15 [−0.13, 0.43] Small or questionable
60% feedback items 0.03 [−0.14, 0.20] Small or questionable
ReST Ballard et al. (2010)  3 1 Less complex pseudowords (PVI duration) 0.84 [0.62, 1.00] Large
Real words (PVI duration) 0.13 [−0.21, 0.47] Small or questionable
Linguistic Integrated Phonological Awareness Intervention Moriarty and Gillon (2006)  3 3 NR NR NA NA
McNeill et al. (2009a)  12 3 Untrained PPC 0.80 [0.64, 0.88] Large
Note. NA = not applicable; MFF = moderate frequency feedback; HFF = high frequency feedback.
Note. NA = not applicable; MFF = moderate frequency feedback; HFF = high frequency feedback.×
a Generalization items were individualized for each participant.
Generalization items were individualized for each participant.×
b Baas et al. (2008)  and Strand et al. (2006)  were excluded from IRD because of diagnostic confidence ratings of 4 and 5.
Baas et al. (2008)  and Strand et al. (2006)  were excluded from IRD because of diagnostic confidence ratings of 4 and 5.×
c Three participants in common across two studies.
Three participants in common across two studies.×
×
A Systematic Review of Treatment for Childhood Apraxia of Speech