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What is Aphasia?

Adult Aphasia

Aphasia is a language disorder that results from damage to the portion of the brain that is dominant for language. For most people, this is the left side of the brain. Aphasia usually occurs suddenly, frequently the result of a stroke or head injury, but it may also develop slowly as in the case of a brain tumor. The disorder may involve aspects of language comprehension and/or expression.

Aphasia treatment strives to improve an individual's ability to communicate. The most effective treatment begins early in the recovery process. Major factors that influence the amount of improvement include the cause of the brain damage, the area of the brain that was damaged, the extent of the brain injury, and the age and health of the patient. Additional factors include motivation, handedness, and educational level.

There are many types of aphasia, however, Broca's aphasia and Wernicke's aphasia are two widely studied aphasic syndromes. Broca's aphasia results from damage to the front portion of the language dominant side of the brain. Wernicke's aphasia results from damage to the back portion of the language dominant side of the brain.

Individuals with Broca's aphasia may speak in short, meaningful sentences. They often omit small words such as "as," "and," and "the." Persons with Wernicke's aphasia may speak in long sentences that have no meaning and often add unnecessary words and create new words. Patients with Broca's aphasia are able to comprehend much of the speech of others, but patients with Wernicke's aphasia have notable difficulties understanding speech.

A third type of aphasia, global aphasia, results from damage to a large portion of the language dominant side of the brain. Individuals with global aphasia have major communication difficulties and may be extremely limited in their ability to speak or comprehend language.

Until recently, little has been known about language organization in the brain of deaf signers. The National Institute on Deafness and Other Communication Disorders (NIDCD) supports research at the Salk Institute, San Diego, California, which has revealed that the left side of the brain is dominant not only for spoken language but for sign language as well. This discovery is particularly interesting since the right side of the brain is dominant for visual and spatial functions. American Sign Language, which is similar in structure to spoken language, is conveyed through hand movements which are visually and spatially oriented. Signers with damage to the right side of the brain had no aphasia for sign language but had difficulty with nonlanguage visual and spatial tasks such as drawing a face. This suggests that, as in those who use spoken language, the right hemisphere in deaf signers develops specialization for nonlanguage visual and spatial functions.

In addition, this research concluded that deaf signers with damage to the left side of the brain demonstrated sign language aphasias similar to the aphasias experienced by those who use spoken language. If the damage was to the front portion of the left side of the brain, the signing would be broken and simplified, much like the broken, effortful speech characteristic of Broca's aphasia. Signers with damage in the back portion of the left side of the brain had fluent signing but poor word selection as well as difficulty understanding the signs of others. This is similar to the word selection and comprehension problems experienced by those with Wernicke's aphasia.

NIDCD-supported researchers at the University of California at San Diego are studying how damage to specific areas of the brain affects language function across different languages. The characteristics of Broca's and Wernicke's aphasias, for example, may differ across languages primarily because of differences in the languages themselves. At the same time, however, similarities may be found. Results of these cross-language studies suggest that language knowledge is preserved in both Broca's and Wernicke's aphasias but difficulty arises in how the language is accessed and used. This is contrary to the present theory that Broca's and Wernicke's aphasias are primarily disorders of language structure.

A number of methods are used to treat aphasia. Health professionals who treat aphasia must select the most effective method of treatment to maximize the aphasic patient's recovery of language function. NIDCD-supported scientists at the Boston University Aphasia Research Center have studied the use of CT scans (computed tomography) to predict the success of one method of treatment, Melodic Intonation Therapy. This form of treatment has been successful for some patients with little or no verbal language following brain injury. The results of this study indicate that information from the CT scan together with results of language assessment by a speech-language pathologist may accurately predict whether this treatment will improve the ability to communicate. Continued research will investigate the use of CT scans, coupled with language tests, to predict the success of other aphasia treatments.

Even with therapy, individuals with severe aphasia may have difficulty communicating even the simplest ideas and needs. Scientists at the University of Maryland Medical System in Baltimore have been investigating the use of a nonverbal method of communication for the aphasic patient called computerized visual communication or C-VIC. This method of communication uses pictures on a computer that represent various parts of speech. Seven patients with either severe Broca's aphasia or global aphasia have recently received training with C-VIC. Six of these patients were able to learn to use the pictures to communicate. The noun pictures were easier for the patients to learn to use than were the verb or action pictures. The information gathered from this research should improve the understanding of the processes underlying language as well as improve the design of speech therapy programs and nonverbal communication systems for individuals with aphasia.

Many professionals who work with aphasic patients believe that it is easier for younger individuals to recover language skills than it is for older individuals. Solid evidence for this concept, however, is lacking. Scientists at the New York University Medical Center in New York City are presently studying how age affects the ability of 90 treated aphasic individuals to relearn language. These individuals range from 50 to 80 years of age and receive comprehensive therapy including speech therapy. It is hoped that the information gained from this study will help select appropriate patients for therapy as well as add to the understanding of how age relates to aphasia.

The NIDCD is one of the institutes of the National Institutes of Health (NIH). The NIDCD conducts and supports biomedical and behavioral research and research on normal and disordered mechanisms hearing, balance, smell, taste, voice, speech and language.

This series is intended to inform health professionals, patients, and the public about progress in understanding the normal and disordered processes of human communication through recent advances made by NIDCD-supported scientists.

For additional information on aphasia call or write:

NIDCD Information Clearinghouse
1 Communication Avenue
Bethesda, Maryland 20892-3456
1-800-241-1044 (Voice)
1-800-241-1055 (TTY/TDD/TT)

Information provided by NIH.