Aphasia
A condition, caused by neurological damage or disease, in which a person's previous capacity to understand or express language is impaired.
In aphasia, the ability to understand language and to translate thoughts into words has been impaired by injury to the brain. Speaking, listening, reading, or writing capabilities may be affected depending on the type of aphasia involved. In children, head injuries, cerebral tumors, brain infection, or other neurological diseases are the most common causes. (Aphasia is also common among older adults, caused primarily by stroke, brain tumor, or degenerative neurological diseases such as Alzheimer's disease.) Aphasia does not include those neurological problems that affect the physical ability to speak or perform the linguistic functions of reading and writing. Aphasia affects one's capacity to manipulate speech sounds, vocabulary, grammar, and meaning. The understanding of aphasia has been enhanced by the development of diagnostic techniques such as magnetic resonance imaging (MRI).
Most cases of aphasia are caused by damage to the left hemisphere of the brain, which is the dominant language hemisphere for approximately 95% of right-handed people and 60-70% of left-handed people.
There are several different types of aphasia, each with different symptoms and each caused by damage to a different part of the brain.
It is possible for children with moderate aphasia following a head injury or other neurological event to recover some of their language abilities with the aid of a speech pathologist. However, if the damage is severe, there is less chance that language abilities will be recovered.
Classifications of Aphasia
Broca's aphasia. This aphasia is characterized by slow, labored, "telegraphic" speech with prepositions and articles missing ("I went store."), but with little or no effect on comprehension of written and spoken language. It affects the frontal lobe of the left hemisphere of the brain. Known as Broca's area, this part of the brain is named for Paul Broca (1824-1880), a 19th-century French physician who studied the specialized functioning of the left and right sides of the brain.
Wernicke's aphasia. In Wernicke's aphasia, the person's speech is overflowing with words (logorrhea) that do not convey the speaker's meaning. The pitch and rhythm of the spoken words sound normal, but the words may either be used incorrectly or are made-up words with no meaning (aphasic jargon). Besides their speech difficulties, persons with Wernicke's aphasia also have trouble comprehending language, repeating speech, naming objects, reading, and writing. Wernicke's aphasia results from damage to the upper rear part of the left temporal lobe of the brain, an area that was first described in 1874 by German neurologist Carl Wernicke (1848-1905).
Anomia, or anomic aphasia. This form of aphasia results in a failure to remember the names of people, objects, or places, but with comprehension of written and spoken language unaffected.
Global aphasia. This is caused by widespread damage to the dominant cerebral hemisphere, either left or right, and is characterized by an almost total loss of all types of verbal ability—speech, comprehension, reading, and writing.
Dysphasia. This term describes a general loss of language use.
Dysgraphia. Describes a form of aphasia characterized by problems in performing hand writing; agraphia describes the complete inability to perform hand writing.
Disconnection aphasias. These are a classification of aphasia caused by damage to the connections of Broca's or Wernicke's areas to each other or to other parts of the brain. Conduction aphasia results from damage to the fiber bundles connecting the two language areas and is characterized by fluent but somewhat meaningless speech and an inability to repeat phrases correctly. In transcortical sensory aphasia, the connections between Wernicke's area and the rest of the brain are severed, but the area itself is left intact. Persons with this condition have trouble understanding language and expressing their thoughts but can repeat speech without any trouble.
Word deafness. This condition occurs when auditory information is prevented from reaching Wernicke's area of the brain. Persons affected by word deafness can hear sounds of all kinds and understand written language, but spoken language is incomprehensible to them, since the auditory signals cannot reach the part of the brain that decodes them.
For Further Study
Books
Eisenson, Jon. Aphasia and Related Disorders in Children. 2nd ed. New York: Harper & Row, 1984.
Howard, David. Aphasia Therapy: Historical and Contemporary Issues. Hillsdale, NJ: Erlbaum, 1987.
Teaching Aphasic Children: The Instructional Methods of Barry and McGinnis. Austin, TX: Pro-Ed, 1988.
Periodicals
Damasio, Antonio R. "Aphasia." The New England Journal of Medicine, February 20, 1992, vol. 326, no. 8, pp. 531+.
Pekkanen, John. "The Boy Who Couldn't Talk." Reader's Digest, January 1988, vol. 132, no. 789, pp. 84.
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