What is apraxia of speech?

Apraxia of speech (AOS)—also known as acquired apraxia of speech, verbal apraxia, or childhood apraxia of speech (CAS) when diagnosed in children—is a speech sound disorder. Someone with AOS has trouble saying what he or she wants to say correctly and consistently. AOS is a neurological disorder that affects the brain pathways involved in planning the sequence of movements involved in producing speech. The brain knows what it wants to say, but cannot properly plan and sequence the required speech sound movements.

AOS is not caused by weakness or paralysis of the speech muscles (the muscles of the jaw, tongue, or lips). The severity of AOS varies from person to person. It can be so mild that it causes trouble with only a few speech sounds or with pronunciation of words that have many syllables. In the most severe cases, someone with AOS might not be able to communicate effectively by speaking, and may need the help of alternative communication methods.

What are the types and causes of apraxia of speech?

There are two main types of AOS: acquired apraxia of speech and childhood apraxia of speech.

  • Acquired AOS can affect someone at any age, although it most typically occurs in adults. Acquired AOS 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. It may result from a stroke, head injury, tumor, or other illness affecting the brain.
  • Childhood AOS is present from birth. This condition is also known as developmental apraxia of speech, developmental verbal apraxia, or articulatory apraxia. Childhood AOS is not the same as developmental delays in speech, in which a child follows the typical path of speech development but does so more slowly than is typical. The causes of childhood AOS are not well understood. Imaging and other studies have not been able to find evidence of brain damage or differences in the brain structure of children with AOS. Children with AOS often have family members who have a history of a communication disorder or a learning disability. This observation and recent research findings suggest that genetic factors may play a role in the disorder. Childhood AOS appears to affect more boys than girls.

 

What are the symptoms of apraxia of speech?

People with either form of AOS may have a number of different speech characteristics, or symptoms:

  • Distorting sounds. People with AOS may have difficulty pronouncing words correctly. Sounds, especially vowels, are often distorted. Because the speaker may not place the speech structures (e.g., tongue, jaw) quite in the right place, the sound comes out wrong. Longer or more complex words are usually harder to say than shorter or simpler words. Sound substitutions might also occur when AOS is accompanied by aphasia.
  • Making inconsistent errors in speech. For example, someone with AOS may say a difficult word correctly but then have trouble repeating it, or may be able to say a particular sound one day and have trouble with the same sound the next day.
  • Groping for sounds. People with AOS often appear to be groping for the right sound or word, and may try saying a word several times before they say it correctly.
  • Making errors in tone, stress, or rhythm. Another common characteristic of AOS is the incorrect use of prosody. Prosody is the rhythm and inflection of speech that we use to help express meaning. Someone who has trouble with prosody might use equal stress, segment syllables in a word, omit syllables in words and phrases, or pause inappropriately while speaking.
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