Childhood Apraxia of Speech (CAS)
Childhood apraxia of speech (CAS) is a neurologically-based motor speech disorder. Children with CAS
have difficulty producing speech sounds in the absence of muscle weakness or paralysis. Though a child with CAS knows what he/she wants to say, impairments in planning and/or coordinating lip, tongue, and jaw movement results in speech sound errors and differences in prosody (patterns of stress and intonation).
CAS is uncommon, occurring in 1-2 children per 1,000. It affects more boys than girls and occurs more frequently in children with galactosemia, fragile X syndrome, and Down Syndrome.
Acquired Apraxia of Speech versus CAS
There are two main types of apraxia of speech: acquired and developmental. Acquired apraxia of speech (AoS) is caused by damage to the parts of the brain involved in speech production and involves loss or impairment of existing speech skills. Causes of AoS include stroke, head injury, tumor, or illnesses affecting the brain. This disorder may occur with muscle weakness affecting speech production or language difficulties caused by brain damage. In contrast, CAS is present from birth and occurs in the absence of any muscle weakness or paralysis.
Cause of CAS
The cause of CAS is yet unknown. While some researchers believe that CAS is a disorder related to overall language development, others believe it is neurologically based and that it disrupts the brain’s ability to send signals to move muscles involved in speech production. Recent research also suggests a genetic component to this disorder, as children with CAS often have family members with a history of communication disorders or learning disabilities.
There is no universally agreed-upon list of diagnostic features that differentiates CAS from other childhood speech sound disorders such as phonological disorders or dysarthria. However, three characteristics of CAS are generally accepted by researchers and speech-language professionals:
- Inconsistent speech sound errors on consonants and vowels across repeated productions of syllables or words. While a child with an phonological or articulation disorder may make the same error each time he/she says a particular word, a child with CAS will not demonstrate a consistent pattern in his/her errors, even when repeating the same word.
- Longer and disrupted coarticulatory transitions between sounds and syllables. Children with CAS have difficulty combining sounds to form a word and may produce long pauses between sounds.
- Differences in prosody. Children with CAS produce speech that sounds choppy or monotonous, with stress on the wrong syllables.
Other Possible Signs/Characteristics of CAS
- No cooing or babbling as an infant
- Late development of first words
- Production of limited set of consonant and vowel sounds
- Numerous substitutions, deletions, and distortions of sounds
- Understands language significantly more than can speak
- Difficulty imitating speech, but imitated speech is more clear than spontaneous speech
- Groping behavior when attempting to produce sounds
- Saying longer words or phrases are more difficult to produce than shorter ones
- Difficult for listeners to understand speech
- Speech sounds choppy or monotonous or the wrong syllables are stressed
- Distorted or inconsistent vowels
Possible Concomitant Conditions:
- Language delay
- Word finding or word order difficulties
- Fine motor coordination difficulties
- Oral hypersensitivity
- Difficulty learning to read, spell, and write
Treatment of CAS:
Children with CAS receive frequent and intensive one-on-one therapy, tailored to their specific speech and language needs. Treatment focuses on improving speech imitation skills, speech-based motor sequences, length and complexity of producible syllable patterns, teaching rules of speech sound patterns, and, in severe cases, using augmentative communication systems (e.g., picture exchange communication system).
If you believe that your child shows signs of CAS or another speech sound disorder, do not hesitate to consult with a speech-language pathologist.