This three-part article series will cover:
- The definition of CAS and who has it (Part I)
- The specific characteristics that distinguish CAS from other speech disorders (Part II)
- What parents might look for in the treatment of CAS (Part III)
What Is CAS?
CAS is an official term recommended by the American-Speech-Language-Hearing Association (ASHA). However, CAS may be referred to as “verbal dyspraxia” in other parts of the world (outside of the USA). Children with CAS/verbal dyspraxia have problems sequencing, coordinating, and timing mouth and vocal movements for speech.
According to ASHA (2007, p. 6), CAS is “a neurological childhood (pediatric) speech sound disorder, in which the precision and consistency of movements underlying speech are impaired in the absence of neuromuscular deficits.” However, children with neuromuscular deficits (e.g., cerebral palsy and Down syndrome) can also have CAS. This is very confusing for both parents and professionals.
Who Has CAS, and How Is It Different From Childhood Dysarthria?
Children born with cerebral palsy, Down syndrome, or other neuromuscular disorders have muscle tone and muscle function problems that often result in a speech difficulty called childhood dysarthria. These children frequently have distorted sounding speech (the main characteristic of dysarthria). Although distorted, their speech sounds fairly consistent regardless of:
- The length of words or sentences, and
- Whether or not they are asked to imitate speech.
Childhood dysarthria is different from CAS. Yet, children with neuromuscular disorders can have CAS in addition to childhood dysarthria.
There are also many children without specific neuromuscular deficits who have CAS. These children have generally adequate muscle tone and muscle function for speech (e.g., children with autism or no specific diagnosis). They do not have any documented brain injury or damage.
So, Why Do Children Have CAS?
Overall, children with CAS do not seem to be using the motor programming area of the brain as well as other children. They do not practice speech like other children in order to develop appropriate sequencing, timing, and coordination of speech. Children need to “babble, babble, babble” and “practice, practice, practice” speech sound combinations in order to develop speech. The premotor cortex (in the frontal lobe of the brain) is believed to be primarily responsible for this process.
Children with neuromuscular disorders (e.g., Down syndrome, cerebral palsy) do not move like other children, so they may not be properly using the premotor cortex to set down adequate motor programs for speech in the first place. Children with generally adequate muscle tone for speech (e.g., children with autism or no specific disorder) may have an inherent weakness in the functioning of the premotor cortex which keeps them from developing adequate sequencing, timing, and coordination for speech. Brain research using functional MRI and PET (positron emission tomography) may ultimately reveal differences and/or similarities in brain function in these two groups of children who can have CAS.
In summary, children with CAS:
- Do not seem to be using the motor programming area of the brain as well as other children
- Do not practice speech like other children
- Do not develop adequate sequencing, timing, and coordination for speech
- Can have childhood dysarthria in addition to CAS
In Part II, we will explore the specific characteristics of CAS which distinguish it from other speech disorders.
American Speech-Language-Hearing Association. (2007). Childhood Apraxia of Speech [Technical Report].