Speech is an important function of the main area of the brain. Three common speech problems that may be caused by damage to the brain or nervous system are:

• Aphasia, which is the loss of the ability to understand, process, or express language. Nonfluent or expressive aphasia is the loss of the ability to express thoughts in speech or writing. Fluent or receptive aphasia is the loss of the ability to understand spoken or written speech. The most common causes of aphasia are stroke or transient ischemic attack (TIA).
• Dysphonia, which is a speech disorder that gives a hoarse quality to the voice. It can be caused by an injury to the nerve that affects the voice box (larynx) or a tumor in the brain stem. It also has other possible causes that are not related to nervous system problems.
• Dysarthria, which is a problem with pronunciation and the rhythm of speech. A person with this problem may seem to stumble over words. This symptom may be caused by a degenerative disease, such as parkinsonism or myasthenia gravis.