Aphasia is a condition characterized by either partial or total loss of the ability to communicate, either verbally or through written words. A person with aphasia may have difficulty speaking, reading, writing, recognizing the names of objects, or understanding what other people have said. Aphasia is caused by a brain injury, as may occur during a traumatic accident or when the brain is deprived of oxygen during a stroke. It may also be caused by a brain tumor, a disease such as Alzheimer's, or an infection, like encephalitis. Aphasia may be temporary or permanent.
Stroke is the most common cause of aphasia in the United States. Approximately 500,000 individuals suffer strokes each year, and 20% of these individualsdevelop some type of aphasia. Other causes of brain damage include head injuries, brain tumors, and infection. About half of the people who show signs ofaphasia have what is called temporary or transient aphasia and recover completely within a few days. An estimated one million Americans suffer from some form of permanent aphasia.
According to the traditional classification scheme, each form of aphasia is caused by damage to a different part of the left hemisphere of the brain.
- The traditional classification scheme includes eight types of aphasia:
- Broca's aphasia, also called motor aphasia, results from damage to the frontportion or frontal lobe of the language-dominant area of the brain. Individuals with Broca's aphasia may either be completely unable to use speech (mutism) or they may be able to use single-word statements or even full sentences.However, these sentences are construct with great difficulty. Hearing comprehension is usually not affected, so they are able to understand other people'sspeech and conversation and can follow commands. Often, weakness on the right side of their bodies makes it difficult to write. Reading ability is impaired. Individuals with Broca's aphasia may become frustrated and depressed because they are aware of their language difficulties.
- Wernicke's aphasiais caused by damage to the side portion or temporal lobe of the language-dominant area of the brain. Individuals with Wernicke's aphasia speak in long, uninterrupted sentences; however, the words used are frequently unnecessary oreven made-up. They may be unable to understand other people's speech. Reading ability is diminished, and although writing ability is retained, what is written may be abnormal. No physical symptoms, such as the right-sided weaknessseen with Broca's aphasia, are typically observed. Also, in contrast to Broca's aphasia, individuals with Wernicke's aphasia are not aware of their language errors.
- Global aphasia is caused by widespread damage to the language areas of the left hemisphere. As a result, all basic language functionsare affected, but some areas may be more affected than others. For example,an individual may have difficulty speaking but may be able to write well. Theindividual may experience weakness and loss of feeling on the right side oftheir body.
- Conduction aphasia, also called associative aphasia, is rather uncommon. Individuals with conduction aphasia are unable to repeat words, sentences, and phrases. Speech is fairly unbroken, although individuals may frequently correct themselves and words may be skipped or repeated. Although able to understand spoken language, it may also be difficult for the individual with conduction aphasia to find the right word to describe a person or object. The impact of this condition on reading and writing ability varies. Aswith other types of aphasia, right-sided weakness or sensory loss may be present.
- Anomic or nominal aphasia primarily influences an individual'sability to find the right name for a person or object. As a result, an objectmay be described rather than named. Hearing comprehension, repetition, reading, and writing are not affected, other than by this inability to find the right name. Speech is fluent, except for pauses as the individual tries to recall the right name. Physical symptoms are variable, and some individuals haveno symptoms of one-sided weakness or sensory loss.
- Transcortical aphasia is caused by damage to the language areas of the left hemisphere outsidethe primary language areas. There are three types of aphasia: transcortical motor aphasia, transcortical sensory aphasia, and mixed transcortical aphasia.Transcortical aphasias are distinguished from other types by the individual's ability to repeat words, phrases, or sentences. Other language functions may also be impaired to varying degrees, depending on the extent and particularlocation of brain damage.
Following brain injury, an initial bedside assessment is made to determine whether language function has been affected. If the individual experiences difficulty communicating, attempts are made to determine whether this difficultyarises from impaired language comprehension or an impaired ability to speak.A typical examination involves listening to spontaneous speech and evaluatingthe individual's ability to recognize and name objects, comprehend what is heard, and repeat sample words and phrases. A speech pathologist or neuropsychologist may be asked to conduct more extensive examinations using in-depth, standardized tests. The results of these tests indicate the severity of the aphasia and may also provide information regarding the exact location of the brain damage. This more extensive testing is also designed to provide the information necessary to design an individualized speech therapy program.
Initially, the underlying cause of aphasia must be treated or stabilized. Toregain language function, therapy must begin as soon as possible following the injury. Although there are no medical or surgical procedures currently available to treat this condition, aphasia resulting from stroke or head injury may improve through the use of speech therapy. For most individuals, however,the primary emphasis is placed on making the most of retained language abilities and learning to use other means of communication to compensate for lost language abilities.
The degree to which an individual can recover language abilities is highly dependent on how much brain damage occurred and the location and cause of the original brain injury. Other factors include the individual's age, general health, motivation and willingness to participate in speech therapy, and whetherthe individual is left or right handed. Language areas may be located in both the left and right hemispheres in left-handed individuals. Left-handed individuals are, therefore, more likely to develop aphasia following brain injury, but because they have two language centers, may recover more fully becauselanguage abilities can be recovered from either side of the brain. The intensity of therapy and the time between diagnosis and the start of therapy may also affect the eventual outcome.