Currently, there is no validated list of diagnostic features differentiating CAS from other childhood speech sound disorders, including those due to phonological-level delay or neuromuscular disorder (dysarthria). However, three segmental and suprasegmental features consistent with a deficit in the planning and programming of movements for speech have gained some consensus among those investigating CAS:
- inconsistent errors on consonants and vowels in repeated productions of syllables or words,
- lengthened and disrupted coarticulatory transitions between sounds and syllables,
- inappropriate prosody, especially in the realization of lexical or phrasal stress.
"Importantly, these features are not proposed to be the necessary and sufficient signs of CAS" (ASHA, 2007a, Definitions of CAS section, para. 1). The frequency of these and other signs may change depending on task complexity, the age of the child, and the severity of symptoms (Lewis, Freebairn, Hansen, Iyengar et al., 2004).
Characteristics that have been reported in children diagnosed with CAS and that represent the difficulty with planning and programming movement gestures for speech include:
- high incidence of vowel distortions;
- limited consonant and vowel phonetic inventory in young children;
- frequent sound distortions and distorted consonant substitutions;
- initial consonant deletions;
- voicing errors;
- schwa additions/insertions to consonant clusters, within words and on the ends of words;
- predominant use of simple syllable shapes;
- greater ease in producing automatic (e.g., frequently used phrases, such as "I love you") versus volitional utterances (e.g., novel phrase or sentence);
- difficulty with smooth, accurate movement gestures;
- better performance on speaking tasks that require single postures versus sequences of postures (e.g., single sounds such as [a] vs. words such as [mama]);
- difficulty achieving accurate articulatory movement gestures when trying to imitate words not yet mastered;
- presence of groping behaviors when attempting to produce speech sounds or coordinate articulators for purposeful movement;
- altered and/or inconsistent suprasegmental characteristics (rate, pitch, loudness);
- increased difficulty with longer or more complex syllable and word shapes (often resulting in omissions, including word-initial consonant deletion);
- predominant errors of consonant, vowel, syllable, and/or word omissions;
- atypical levels of regression (e.g., words or sounds mastered, then lost);
- sequencing errors affecting sounds (e.g., metathesis, migration), syllables, morphemes, or words.
(Campbell, 2003; Caruso & Strand, 1999; Davis et al., 1998; Davis & Velleman, 2000; McCabe, Rosenthal, & McLeod, 1998; Shriberg et al., 1997; Strand, Shriberg, & Campbell, 2003)
The presence of error patterns in the child's speech does not indicate a phonological rather than motoric problem. Many patterns can have either linguistic or motoric bases. For example, a child may consistently reduce consonant clusters either because of lack of understanding of the phonological rule or because of a motoric inability to sequence consonants.
The behavioral features reportedly associated with CAS place a child at increased risk for problems in expressive language and weakness in the phonological foundations for literacy (Lewis, Freebairn, Hansen, Iyengar et al., 2004; McNeill, Gillon, & Dodd; 2009a). These problems may reflect the consequences of CAS, nonrelated co-occurring problems (e.g., learning disabilities and attentional difficulties), or even the effects of compensatory strategy use and include
- delayed language development;
- expressive language problems, like word order confusion and grammatical errors;
- problems when learning to read, spell, and write (literacy);
- problems with social language/pragmatics.
Nonspeech sensory and motor problems include
- gross and fine motor delays;
- motor clumsiness, oral apraxia;
- limb apraxia;
- feeding difficulties;
- abnormal orosensory perception (hyper- or hyposensitivity in the oral area).
(Crary & Anderson, 1991; Davis et al., 1998; Dewey, Roy, Square-Storer, & Hayden (1988); McCabe et al., 1998; Shriberg et al., 1997)