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Cochrane Database of Systematic Reviews Protocol - Intervention

Intervention for developmental apraxia of speech

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Abstract

This is a protocol for a Cochrane Review (Intervention). The objectives are as follows:

To assess the efficacy of intervention for developmental apraxia of speech / developmental verbal dyspraxia.

Background

Morley, Court and Miller (Morley 1954) provided a seminal paper documenting a series of speech characteristics in children that resembled the speech production disorder of adults with acquired apraxia of speech. There are various terms used today to denote this cluster of developmental apraxic speech symptoms in children, however the most common nosology includes the terms Developmental Verbal Dyspraxia (DVD), and Developmental Apraxia of Speech (DAS).

There are no epidemiological data currently available on the prevalence of DAS, although it occurs infrequently in comparison with other forms of developmental speech disorder (e.g., phonological disorder). The aetiology of DAS is also largely unknown but ‐ as with other forms of speech and language disorder (Bishop 1996; Lewis 1992; Tallal 1991; Scheffer 2000) ‐ a familial link has been reported (Lewis 2004). The potential for heritability of the disorder has been confirmed in one particular subgroup where DAS is reported to develop subsequent to genetic disruption of the FOXP2 gene (Vargha‐Khadem 1995; Vargha‐Khadem 1998).

In relation to the diagnosis of DAS, clinicians are unable to agree on the ultimate discriminating features or assessment tasks for differentiating the disorder from other forms of developmental speech impairment. There is some consensus on the features of DAS however, including: the presence of articulatory struggle (groping), particularly at the beginning of words; substitution errors; markedly inconsistent production on repetitions of the same word; increased phoneme and syllable deletions; increased vowel/diphthong errors; and prosodic disturbance (Austin 1996; Forrest 2003).

Despite the disorder being reported over fifty years ago, neither the diagnostic features nor the underlying cause of the disorder can be agreed upon (Shriberg 1997). In particular, whether the developmental form of apraxia of speech is due to an underlying linguistic or motor deficit or a combination of both is heavily debated. It has been difficult to dissociate motor and linguistic features of verbal dyspraxia because lexical, phonological and articulation deficits co‐occur and are commonly assessed simultaneously during a clinical evaluation due to the very nature of the assessment tasks (Maassen 2002).

There is also little knowledge of how DAS changes across time, although younger children present with more severe forms of the disorder with improvement over time in the presence of persistent irregular consonant, vowel and syllable‐level errors (Davis 2005; Jacks 2006). It is not known how age, or severity of DAS impact upon treatment success.

Historically, DAS was reported to be a disorder of motor programming, whereby children were unable to accurately program the sound sequences required to produce accurate speech. Initial treatment approaches were subsequently motor‐based in line with the proposed underlying basis of the impairment. One of the earliest treatment methods still advocated in recent times is a form of traditional articulation‐based drill therapy (Velleman 1994). In this form of treatment the child is first taught to produce a sound in isolation (e.g., /r/) using a drill‐based approach, and is then required to combine this newly acquired phoneme with a range of high‐frequency use vowels in syllables. Gradually, with increasing performance success, the number of syllables in a word is increased. Theoretically this treatment is designed to improve a child's motor programming abilities using drill practice to automatise or store sound sequences, presumably helping them to access sound sequences more easily in future. This model is well aligned with the model of speech production proposed by Levelt (Levelt 1999) whereby the complex act of speech is achieved through rapid access to a set of stored frequently used syllables. Other motor‐based approaches reported in the literature include rate control therapy (Rosenthal 1994) and electropalatography (Carter 2004).

In recent times however, with little consensus on the underlying nature or diagnosis of DAS, the number of treatment investigations and newly proposed treatment types has been severely limited. The underlying hypotheses supporting existing interventions have been widespread, making it difficult to group the treatment types. At a broad level, one subgrouping consists of perceptually‐based therapy approaches such as traditional articulation or phonological therapy, the PROMPT System (Prompts for restructuring oral muscular phonetic targets) (Chumpelik 1984), melodic intonation therapy (Helfrich‐Miller 1994), ACT (adapted cueing technique) (Klick 1985), oral form recognition training (Kingston 1987), orofacial myofunctional therapy (Ray 2003), and rate control therapy (Rosenthal 1994). A second subgroup consists of more instrumentally‐based biofeedback treatments including delayed auditory feedback (Lozano 1978) and electropalatography (Carter 2004). A review of treatment for DAS has not been conducted for over fifteen years (Pannbacker 1988). Furthermore, the original review by Pannbacker (Pannbacker 1988) is anecdotal, being based on clinical experience or reports from experts within the field. In summary, there has been no systematic review of the efficacy of treatment for DAS to date.

Whilst DAS requires further refinement in relation to consensus on diagnostic features and the underlying correlates, children requiring treatment continue to present with the disorder, and there is a need for clinicians to be aware of the evidence base of treatments, and which are the most efficacious. This paper aims to systematically review the evidence for the efficacy of perceptual and instrumentally‐based biofeedback treatment types for children and adolescents with DAS.

Objectives

To assess the efficacy of intervention for developmental apraxia of speech / developmental verbal dyspraxia.

Methods

Criteria for considering studies for this review

Types of studies

Randomised controlled trial (RCT) studies and and quasi‐randomised studies will be included (e.g., studies in which participants were allocated on alternate days).

Types of participants

Children aged 3‐16 years diagnosed with developmental apraxia of speech / developmental verbal dyspraxia.

Types of interventions

1) Perceptually‐based therapy: Intervention using traditional drill exercises, typically in the absence of instrumentation, and often without feedback other than auditory feedback, e.g., traditional articulation or phonology based treatment, prosodic or intonation therapy, the PROMPT System (prompts for restructuring oral muscular phonetic targets)
(Chumpelik 1984), rate control therapy (Rosenthal 1994), orofacial myofunctional therapy (Ray 2003), and melodic intonation therapy (Helfrich‐Miller 1994).
2) Instrumentally‐based biofeedback approaches: Interventions that use some form of instrumentation and that typically also provide visual or other forms of biofeedback in addition to auditory feedback (e.g., electropalatography (Carter 2004).

Control groups may be waitlist control or no treatment control.

Types of outcome measures

Three levels of outcomes will be considered for analysis used to measure change in speech production (Law 2003):
1. At the isolated function level of speech production, e.g. an increase in sounds represented in a phonetic inventory; decreased frequency of omission, substitution or addition phonetic errors.
2. At the single word or sentence level of general speech production, e.g. improvement in overall speech prosody pattern as measured via profiles of lexical and sentential stress (e.g., based on measures such as vowel duration, fundamental frequency at vowel midpoint, timing of fundamental frequency peak relative to vowel onset, etc).
3. At the broader level of speech production where outcomes demonstrate functional gains in communication, e.g. improvements noted in the intelligibility of spontaneous speech as rated via clinicians or blind‐raters, or as reported by child or parental questionnaires on speech function.

Both standardised and informal outcome measures will be evaluated, including clinician, parent or child questionnaire reports on outcome.

Search methods for identification of studies

The following databases will be searched from inception:

Cochrane Central Register of Controlled Trials (CENTRAL), published in The Cochrane Library
MEDLINE
CINAHL
Dissertation Abstracts
EMBASE
ERIC
Linguistics and Language Behaviour Abstracts (LLBA)
PsycINFO

The search strategy below will be used for MEDLINE:

1 exp Apraxias/
2 dysprax$.tw.
3 aprax$.tw.
4 prax$.tw.
5 (speech adj3 (disorder$ or impair$ or problem$ or difficult$)).tw.
6 ((voice or vocal) adj3 (disorder$ or impair$ or problem$ or difficult$)).tw.
7 (communication adj3 (disorder$ or impair$ or problem$ or difficult$)).tw.
8 or/1‐7
9 (therap$ or train$ or rehabilitat$ or manage$ assist$ or measure$ or treat$ or assess$ or remedia$ or augment$ or recover$ or rehab$).tw.
10 8 and 9
11 Child/
12 (child$ or girl$ or boy$ or pre school$ or pre‐school$).tw.
13 or/11‐12
14 8 and 10 and 13
15 randomized controlled trial.pt.
16 controlled clinical trial.pt.
17 randomized controlled trials.sh.
18 random allocation.sh.
19 double blind method.sh.
20 single‐blind method.sh.
21 or/15‐20
22 (animals not human).sh.
23 21 not 22 (362564)
24 clinical trial.pt.
25 exp Clinical Trials/
26 (clin$ adj25 trial$).ti,ab.
27 ((singl$ or doubl$ or trebl$ or tripl$) adj25 (blind$ or mask$)).ti,ab.
28 placebos.sh.
29 placebo$.ti,ab.
30 random$.ti,ab.
31 research design.sh.
32 or/24‐31
33 32 not 22
34 33 not 23
35 comparative study.sh.
36 exp Evaluation Studies/
37 follow up studies.sh.
38 prospective studies.sh.
39 (control$ or prospectiv$ or volunteer$).ti,ab.
40 or/35‐39
41 40 not 22
42 41 not (23 or 34)
43 23 or 34 or 42
44 14 and 43

Terms and filters will be modified as appropriate for other databases.

We will request information on unpublished trials from authors of published studies, and experts and information groups in the areas of linguistics and speech therapy.

Data collection and analysis

Titles and Selection of trials
Titles and abstracts will be independently screened for inclusion by both authors (AV) and (AM). In cases of uncertainly over whether an abstract meets the inclusion criterion by either author, the full text article will be obtained. Each paper will then be evaluated independently by the two reviewers (AV) and (AM) for inclusion. In the event of disagreement over inclusion of a particular paper, a consensus will be formed by AV and AM re‐assessing the inclusion criterion together.

Quality Assessment
Included trials will be evaluated against a number of criteria. Both reviewers will assess and independently rate the methodological quality of the included studies for the aspects outlined below, using the following three quality codes as described in the Cochrane Collaboration Handbook (Higgins 2005):

(A) Adequate
(B) Component not reported or unclear
(C) Component reported but inadequate

  • Method of allocation: (e.g., Adequate: use of pre‐numbered or coded identical containers administered serially to participants; Unclear: no description of allocation methods; Inadequate: Poor or nil concealment of allocation, e.g., alternate assignment).

  • Blinded to treatment allocation: Were the assessors blind to treatment allocation? (e.g., Adequate: clinician, patient and outcome assessor blinded to allocated treatment group of patient; unclear: blinding of allocation not reported or cannot be verified by contacting investigators/investigators cannot be contacted; Inadequate: clinician, patient or outcome assessor not blinded to allocation group).

  • Proportion of losses to follow up (e.g., Adequate: losses to follow up equally distributed between comparison groups; Unclear: losses to follow up not reported; Inadequate: studies will be excluded where dropout is disproportionate to the remaining study population). Missing data will initially be sought via contact with the corresponding author. In regard to participant drop out, if the rate of attrition reaches a 30% threshold in an included study, the study will be included in the systematic review but not in the meta‐analysis . The maximum allowed difference in the dropout rate between the two groups will be 10% before a study included in the review is excluded from meta‐analysis.

  • Intention‐to‐treat analysis (e.g., Adequate: where all trial participants were included in the final analysis, and analysed in the groups to which they were randomised regardless of : i) treatment type received, and ii) other protocol irregularities; Unclear: Intention‐to‐treat analysis not reported; Inadequate: Not all trial participants included in the final analysis due to protocol irregularities.

Studies rated as (C) will be analysed separately in sensitivity analyses.

Data management
In addition to outcome data, the following information will be documented by both reviewers using a data management form to be developed and piloted: participant details; setting (e.g., community clinic, school, hospital); type of intervention; length and frequency of intervention; professions involved; duration of impairment; level of severity; co‐morbidity; assessment tools employed. Any information that is missing or unclear will be requested from the corresponding author. Outcome data will be independently entered on to RevMan by (AV) and (AM) and a re‐evaluation of the data and entries performed together by AV and AM to reach consensus on points of disagreement.

Missing data
In the event of missing data within published studies, authors AM and AV will contact primary investigators for assistance and information.

Data synthesis
Meta‐analysis will be only performed where studies employ similar interventions and where study populations are clinically homogenous.

Continuous data
To enable the combination of studies measuring the same outcome using different methods, continuous data will be summarised using standardised mean differences.

Binary data
Binary outcomes are likely to be common in early reports within the field (e.g., improved outcome vs no change/worse). Data will be analysed by calculation of the relative risk with a 95% confidence interval.

Subgroup analysis
If possible, subgroup analysis will be undertaken by age group, site of brain lesion, severity of brain injury (measured via the Glasgow Coma Scale), the severity of dysarthria

Sensitivity analysis
Sensitivity analysis will be used to assess the robustness of the overall findings by examining the impact of study quality, e.g. lack of allocation concealment or high rates of loss to follow‐up, the impact of missing data or the impact of imputations, and the rigor of eligibility criteria employed in the study.

We will also evaluate the possibility of one or more large studies dominating the results.

Investigation of heterogeneity
Consistency of results will be assessed by examining I2 (Higgins 2002). I2 is a quantity describing approximately the proportion of variation in point estimates that is due to heterogeneity of a sample rather than error in sampling of the population. A test of homogeneity will be used to determine that the heterogeneity is genuine. In the event of too few studies being available to make this test feasible, a random effects model will be applied.

Assessment of bias
Where appropriate, the possibility that the study selection was affected by bias will be assessed using funnel plots to investigate any relationship between effect size and study precision (closely related to sample size). Such a relationship could be due to publication or related biases or due to systematic differences between small and large studies, or a statistical artefact of the chosen effect measure.