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Key characteristics of CAS

When considering characteristics of the disorder, SLPs need to keep in mind that children with other speech sound disorders share some characteristics from the list. Other characteristics may be more common and contribute more specifically to the differential diagnosis of CAS, distinguishing CAS from the other pediatric speech sound disorders. Additional research is needed to identify a diagnostic marker with an acceptable degree of specificity and sensitivity (i.e.: identifies children with CAS while ruling out those who do not have CAS). Until such research data is available, the list below may be useful for identification of children suspected to have CAS.

Key characteristics:

  • Limited repertoire of vowels; less differentiation between vowel productions; and vowel errors, especially distortions
  • Variability of errors
  • Unusual, idiosyncratic error patterns (sometimes defying transcription!)
  • Errors increase with length or complexity of utterances, such as in multi-syllabic or phonetically challenging words.
  • Depending on level of severity, child may be able to produce accurately the target utterance in one context but is unable to produce the same target accurately in a different context.
  • More difficulty with volitional, self-initiated utterances as compared to over-learned, automatic, or modeled utterances
  • Impaired rate/accuracy on diodochokinetic tasks (Alternating movement accuracy or maximum repetition rate of same sequences such as /pa/, /pa/, /pa/ and multiple phoneme sequences such as /pa/ /ta/ /ka/ )
  • Disturbances of prosody including overall slow rate; timing deficits in duration of sounds and pauses between and within syllables contributing to the perception of excess and/or equal stress, “choppy” and monotone speech.
  • At some point in time, groping or observable physical struggle for articulatory position may be observed (possibly not present on evaluation, but observable at some point in treatment).
  • May also demonstrate impaired volitional nonspeech movements (oral apraxia)

Other characteristics that may describe children with CAS, but are less likely to contribute to a differential diagnosis include:

  • Poor speech intelligibility
  • Delayed onset of speech
  • Limited babbling as an infant
  • Restricted sound inventory
  • Loss of apparently previously spoken words

Note that at the current time, SLPs do not demonstrate consistency in which characteristics they place more weight on than others in the diagnosis of CAS. Nor is it clear which or how many characteristics must be present for the diagnosis. Thus, SLPs must use a great deal of clinical judgment in diagnosis. (For more information see Forrest. K. (2003) Diagnostic criteria of development apraxia of speech used by clinical speech-language pathologists. American Journal of Speech-Language Pathology, 12(3), pp. 376 – 380.)