Childhood apraxia of speech (CAS), also known as developmental verbal dyspraxia (DVD), is a relatively rare speech disorder in which children have difficulty producing the sounds of speech. What makes CAS different from other speech disorders is that a child knows the sound she wishes to create, but is unable to do so due to a neurological abnormality. In CAS, a miscommunication exists between the brain and the muscles of speech. This leads to the production of sounds that are inaccurate and that appear to be produced at random. Over half of children with autism are thought to struggle with CAS.
In addition to getting speech signals crossed, children with CAS have great difficulty consistently and accurately making the sounds to form words. One minute, they may try to say “ma” and it sounds like “va.” The next, it sounds like “vo”. CAS is distinguished from other speech disorders such as difficulty in physically pronouncing certain sounds (e.g., “r”, “th”, “s”), which can be caused by muscle, lack of coordination, or an inability to accurately distinguish a sound. Instead, a child with CAS knows exactly which sound they wish to produce, but cannot get their muscles to produce that sound accurately or consistently. As a result, a child may wish to say “brother” but may instead produce the sounds “ma” or “my” or “fo”, seemingly at random.
Whereas a child with a lisp or other speech problem may be unintelligible to strangers but not their parents, children with CAS may be even incomprehensible to their parents because of the randomness of their word-sounds. Lack of consistency in sound production for any particular word or sound is a hallmark of CAS. Children may also sound “choppy” or have a weird “melody” or “rhythm” to their speech pattern called inappropriate or disordered prosody. They may also “grope” for words, meaning that a child may struggle to form a sound before any sound is produced.
Although CAS is of neurological origin, it cannot yet be diagnosed with typical neurological brain scans. Children with CAS often have other language and developmental delays, and it is sometimes difficult to distinguish between ultimate causes. The disorder may be the result of a stroke or traumatic brain injury. Emerging research suggests that abnormalities in the FOXP2 gene may increase the risk of CAS.