Apraxia of speech, also known as verbal apraxia or dyspraxia, is a speech disorder in which a person has trouble saying what he or she wants to say correctly and consistently. It is not due to weakness or paralysis of the speech muscles (the muscles of the face, tongue, and lips). The severity of apraxia of speech can range from mild to severe.
There are two main types of speech apraxia: acquired apraxia of speech and developmental apraxia of speech.
Acquired apraxia of speech can affect a person at any age, although it most typically occurs in adults. It is caused by damage to the parts of the brain that are involved in speaking, and involves the loss or impairment of existing speech abilities. The disorder may result from a stroke, head injury, tumor, or other illness affecting the brain. Acquired apraxia of speech may occur together with muscle weakness affecting speech production (dysarthria) or language difficulties caused by damage to the nervous system (aphasia).
Developmental apraxia of speech (DAS) occurs in children and is present from birth. It appears to affect more boys than girls. This speech disorder goes by several other names, including developmental verbal apraxia, developmental verbal dyspraxia, articulatory apraxia, and childhood apraxia of speech. DAS is different from what is known as a developmental delay of speech, in which a child follows the “typical” path of speech development but does so more slowly than normal.
The cause or causes of DAS are not yet known. Some scientists believe that DAS is a disorder related to a child’s overall language development. Others believe it is a neurological disorder that affects the brain’s ability to send the proper signals to move the muscles involved in speech. However, brain imaging and other studies have not found evidence of specific brain lesions or differences in brain structure in children with DAS. Children with DAS often have family members who have a history of communication disorders or learning disabilities. This observation and recent research findings suggest that genetic factors may play a role in the disorder.
People with either form of apraxia of speech may have a number of different speech characteristics, or symptoms, including:
Children with developmental apraxia of speech generally can understand language much better than they are able to use language to express themselves. Some children with the disorder may also have other problems, including:
The severity of both acquired and developmental apraxia of speech varies from person to person. Apraxia can be so mild that a person has trouble with very few speech sounds or only has occasional problems pronouncing words with many syllables. In the most severe cases, a person may not be able to communicate effectively with speech, and may need the help of alternative or additional communication methods.
In some cases, people with acquired apraxia of speech recover some or all of their speech abilities on their own. This is called spontaneous recovery. Children with developmental apraxia of speech will not outgrow the problem on their own. Speech-language therapy is often helpful for these children and for people with acquired apraxia who do not spontaneously recover all of their speech abilities.
Therapy is tailored to the individual and is designed to treat other speech or language problems that may occur together with apraxia. Each person responds differently to therapy, and some people will make more progress than others. People with apraxia of speech usually need frequent and intensive one-on-one therapy. Support and encouragement from family members and friends are also important.
In severe cases, people with acquired or developmental apraxia of speech may need to use other ways to express themselves. These might include formal or informal sign language, a language notebook with pictures or written words that the person can show to other people, or an electronic communication device such as a portable computer that writes and produces speech.