The National Institute of Neurological Disorders and Stroke estimates that 1 million people in the United States suffer from a language disorder called aphasia. With this disorder, patients have sustained damage to areas of the brain that are involved in language, such as
Apraxia of speech, unlike aphasia, affects a patient's speech abilities, not her language abilities. The patient has trouble with the voluntary movement patterns needed to produce speech, though she does not have either weakness or paralysis of the muscles involved in speech. If a patient has acquired apraxia of speech, she has damage to the areas of the brain that are used in speech. Possible causes include a stroke, brain tumor, head injury, dementia and neurodegenerative illnesses. However, some apraxia of speech patients have had the disorder since birth. This type of apraxia of speech is called developmental apraxia of speech; other names include childhood apraxia of speech, developmental verbal apraxia and articulatory apraxia. The cause of developmental apraxia of speech is not known, though the National Institute on Deafness and Other Communication Disorders pointed out that patients may have a family history of either communication disorders or learning disabilities.
Patients with apraxia of speech can have several different speech issues. For example, patients may have problems speaking longer or complex words. MedlinePlus noted that short phrases that a patient uses daily, such as “How are you?” can be said without much issue. Patients can have trouble putting together sounds to say a word correctly. It may take a patient several attempts to say a word before saying it correctly. The National Institute on Deafness and Other Communication Disorders added that a common characteristic in this speech disorder is incorrectly using prosody, which is the stress, rhythm and intonation used when speaking.