Childhood Apraxia of Speech

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Q&A with the author of a paper on motor-based intervention protocols for CAS.

Many of the intervention approaches for childhood apraxia of speech (CAS), a speech motor planning and/or programming disorder, are motor-based. The inclusion of so-called principles of motor learning into treatment for CAS has gained considerable attention in recent years. Few studies, however, have systematically compared different practice conditions directly. “Motor-Based Intervention Protocols in Treatment of Childhood Apraxia of Speech (CAS),” which published in the journal Current Developmental Disorders Reports in April 2014, reviews motor-based treatment approaches for CAS, and highlights current trends and directions for the near future.

ADVANCE for Speech & Hearing staff writer Rebecca Mayer Knutsen spoke with Edwin Maas, PhD, assistant professor in the department of speech, language, and hearing sciences at University of Arizona, who co-authored the paper with Christina Gildersleeve-Neumann, Kathy J. Jakielski and Ruth Stoeckel.

The paper provides a narrative review of a number of specific motor-based treatments for CAS and their empirical evidence base. “Overall, abstracting away from specific treatment approaches because most share a number of features, the conclusion at this time is that motor-based intervention protocols appear to be efficacious,” shared Maas.

ADVANCE: How is CAS diagnosed?

Maas: At present, there is no single validated test or procedure used to diagnose CAS. Diagnosis of CAS is determined by a certified speech-language pathologist, and is based on the presence of three features that have garnered some consensus in the literature, including:1

  • Inconsistent errors on consonants and vowels in repeated productions of the same target utterances.
  • Difficulties with coarticulation and transitions between sounds.
  • Abnormal prosody, in particular for word and sentence stress patterns.

It’s important to note, however, that these features are not operationalized or standardized in terms of speech tasks, target utterances, measures and criterion scores. Several protocols have been proposed in the literature, some of which have been prospectively validated such as a maximal performance task protocol;2 whereas others including the Dynamic Evaluation of Motor Speech Skill are promising.3 A recent article proposed a combination of tasks and measures, namely multisyllabic word production and diadochokinesis.4 Until a test or procedure is available that is prospectively validated on a relatively large, representative, and unselected sample, current best practice is to obtain consensus among experienced speech-language pathologists.

ADVANCE: What are the current treatment trends to improve speech motor skills? Which ones are most successful and why?

Maas: The potential importance of principles of motor learning is gaining attention, and several recent studies have begun to incorporate such principles5-6,15 or directly compare different practice conditions.7-8 Although some of these principles may facilitate learning similar to other domains of motor learning, there is also reason for caution because there are differences between children with respect to what constitute optimal intervention parameters. We expect to see more of such research to optimize treatment outcomes in the next few years.

In terms of specific treatment approaches, several approaches have at least preliminary evidence to support their use, with the strength of the evidence varying across approaches. An integral stimulation based approach (“watch me, listen to me, say what I say”) combined with dynamic cues appears promising, because this general approach has been found to produce treatment effects in at least six well-controlled single-case experimental designs across three different research groups.6-7,16 Although sample sizes have been small to date, the study designs do support causal claims of treatment efficacy. This approach may be effective in part because it combines visual and tactile with auditory cues, incorporates a slower speech rate to ostensibly provide children more time to process the feedback from their movements, and implements a range of motor learning principles.

Evidence for other approaches varies. For example, evidence for Rapid Syllable Transitions treatment, which targets the suprasegmental difficulties often seen in CAS, includes a number of single-case experimental designs and a randomized controlled trial from the same research group. 4-5 As another example, the Prompts for Restructuring Oral Muscular Phonetic Targets (PROMPT) treatment has been found to produce treatment effects for CAS in a single-case experimental design,9 whereas other studies using PROMPT have either explicitly excluded children with CAS or have used pre-post designs that do not support causal claims of efficacy.

Finally, a recent trend that has shown promise for application with children with CAS is the use of biofeedback in treatment. A recent single-case experimental design study used ultrasound biofeedback to target speech sound accuracy in six children with CAS.10 All six children showed improvements attributable to the treatment. It is possible that the visual feedback complements, or allows children to compensate for, disruptions in the use of auditory and somatosensory feedback to control speech movements, as some recent computational simulation studies have suggested.11-12

ADVANCE: What further research is needed for people with this speech disorder?

Maas: A lot of research is still needed in this area. The research needs include studies on developing and validating procedures that will enable a true understanding, and in turn accurate diagnosis of the underlying impairments (and their interactions with other parts of the cognitive and motor systems involved).

The recent development of detailed computational neural network models14 is expected to facilitate this enterprise by enabling more refined hypotheses and ways to test them.12-13

In addition, there is a great need for additional treatment research, with stronger designs (that can support claims of efficacy), larger sample sizes, and an additional focus on functional outcomes and treatment candidacy (what works for whom?). Our article highlights a number of promising directions for optimizing treatment outcomes. Findings from treatment studies can also further inform our understanding of the disorder itself. We expect to see a great deal more research in these areas in the years to come.


References

  1. American Speech-Language-Hearing Association. (2007). Childhood Apraxia of Speech [Technical Report]. Retrieved from http://www.asha.org/policy, March 2011.
  2. Thoonen, G., Maassen, B., Gabreëls, F., & Schreuder, R. (1999). Validity of maximum performance tasks to diagnose motor speech disorders in children. Clinical Linguistics & Phonetics, 13, 1-23.
  3. Strand, E. A., McCauley, R. J., Weigand, S. D., Stoeckel, R. E., & Baas, B. S. (2013). A motor speech assessment for children with severe speech disorders: Reliability and validity evidence. Journal of Speech, Language, and Hearing Research, 56, 505-520.
  4. Murray, E., McCabe, P., Heard, R., & Ballard, K. J. (2015). Differential diagnosis of children with suspected Childhood Apraxia of Speech. Journal of Speech, Language, and Hearing Research, 58, 43-60.
  5. Ballard, K. J., Robin, D. A., McCabe, P., & McDonald, J. (2010). A treatment for dysprosody in childhood apraxia of speech. Journal of Speech, Language, and Hearing Research, 53, 1227-1245.
  6. Strand, E. A., Stoeckel, R., & Baas, B. (2006). Treatment of severe childhood apraxia of speech: A treatment efficacy study. Journal of Medical Speech-Language Pathology, 14, 297-307.
  7. Edeal, D. M., & Gildersleeve-Neumann, C. E. (2011). The importance of production frequency in therapy for childhood apraxia of speech. American Journal of Speech-Language Pathology, 20, 95-110.
  8. Maas, E., & Farinella, K. A. (2012). Random versus blocked practice in treatment for childhood apraxia of speech. Journal of Speech, Language, and Hearing Research, 55, 561-578.
  9. Dale, P. S., & Hayden, D. A. (2013). Treating speech subsystems in childhood apraxia of speech with tactual input: The PROMPT approach. American Journal of Speech-Language Pathology, 22, 644-661.
  10. Preston, J. L., Brick, N., & Landi, N. (2013). Ultrasound biofeedback treatment for persisting childhood apraxia of speech. American Journal of Speech-Language Pathology, 22, 627-643.
  11. Terband, H., Maassen, B., Guenther, F. H., & Brumberg, J. (2009). Computational neural modeling of speech motor control in childhood apraxia of speech (CAS). Journal of Speech, Language, and Hearing Research, 52, 1595-1609.
  12. Terband, H., Maassen, B., Guenther, F. H., & Brumberg, J. (2014). Auditory-motor interactions in pediatric motor speech disorders: Neurocomputational modeling of disordered development. Journal of Communication Disorders, 47, 17-33.
  13. Terband, H., van Brenk, F., & van Doornik-van der Zee, J. C. (2014). Auditory feedback perturbation in children with developmental speech disorders. Journal of Communication Disorders, 51, 64-77.
  14. Guenther, F. H., Ghosh, S. S., & Tourville, J. A. (2006). Neural modeling and imaging of the cortical interactions underlying syllable production. Brain and Language, 96, 280-301.
  15. Maas, E., & Farinella, K. A. (2012). Random versus blocked practice in treatment for childhood apraxia of speech. Journal of Speech, Language, and Hearing Research, 55, 561-578.
  16. Maas, E., Butalla, C. E., & Farinella, K. A. (2012). Feedback frequency in treatment for childhood apraxia of speech. American Journal of Speech-Language Pathology, 21, 239-257.
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Rebecca Mayer Knutsen

Rebecca Mayer Knutsen writes for ADVANCE

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