What is CAS?
Childhood Apraxia of Speech, or CAS for short, is a speech disorder that results in children being unable to form the words they intend to, even though they know what they want to say. It is associated with very low intelligibility and is arguably one of the most frustrating speech challenges kiddos and their parents face. CAS is also sometimes also called Developmental Apraxia, but unlike this name suggests, children do not often improve spontaneously; skilled speech therapy is required to treat it.
Origins of CAS
CAS is estimated to occur in only 1 or 2 of every 1,000 children in America. Unlike acquired apraxia, which is most often seen in adults who have had strokes or traumatic brain injury, the cause of CAS is unknown. Rarely are there any observable differences in the brain, though CAS can sometimes occur as a symptom of a syndrome, genetic disorder, or metabolic condition (e.g., galactosemia). CAS is known to exist at higher rates in children who have other neurodevelopmental conditions such as ADHD, Autism, and epilepsy.
Mechanics of CAS
The act of speech is a series of incredibly precise fine motor skills that requires very refined movement of the lips, tongue, and jaw. If the neurological planning of these movements is disrupted, as in the case of CAS, low intelligibility results. Recent research indicates that children with CAS may have difficulties with sensory feedback loops required to learn and judge the accuracy of speech. Sensory feedback is important for the subliminal knowledge of proximity between speech structures (e.g., lips, tongue, teeth, palate) during speech, which plays a role in execution of movement.
What CAS is Not
CAS does not involve physical issues with the mouth, such as muscle weakness or muscle coordination difficulties. It also does not involve the brain itself, but rather nerve pathways responsible for planning speech movements.
CAS vs Phonological Disorder
Many times, parents of children who exhibit very low intelligibility research causes online and conclude that Childhood Apraxia of Speech is to blame for their child’s unintelligible speech. However, children with severe phonological disorders can be just as unintelligible, or even more so, than children with CAS. Your speech-language pathologist will need to analyze your child’s speech to discern whether distinct error patterns (e.g., deleting or substituting certain sounds in various word positions) are present, as in a phonological disorder, or whether the errors are inconsistent or random, as in CAS. CAS and phonological disorders can also coexist.
Errors related to CAS often change as a word is repeated, and these errors cannot be grouped into categories, unlike phonological errors. Other characteristics of CAS which distinguish it from a severe phonological disorder include errors on vowels, prosodic errors (relating to stress and intonation), increased errors as utterance length increases, and increased errors in spontaneous speech over rehearsed speech. When your child’s speech is evaluated, your speech-language pathologist will provide an appropriate diagnosis in order to follow with appropriate treatment methods.
By Kathleen Winger MS CCC-SLP
