Aphasia (or aphemia) is a loss or impairment of the ability to produce and/or comprehend language, due to brain damage. It is usually a result of damage to the language centres of the brain (like Broca's area). These areas are almost always located in the left hemisphere, and in most people this is where the ability to produce and comprehend language is found. However in a very small number of people language ability is found in the right hemisphere. Damage to these language areas can be caused by a stroke, traumatic brain injury or other head injury. Aphasia may also develop slowly, as in the case of a brain tumor. Depending on the area and extent of the damage, someone suffering from aphasia may be able to speak but not write, or vice versa, understand more complex sentences than he or she can produce, or display any of a wide variety of other deficiencies in reading, writing, and comprehension.

Aphasia may co-occur with speech disorders such as dysarthria or apraxia of speech, which also result from brain damage.

Aphasia can be assessed in a variety of ways, from quick clinical screening at the bedside to several-hour-long batteries of tasks that examine the key components of language and communication.

The common types of aphasia are

• Broca's aphasia (expressive aphasia)
• Wernicke's aphasia (receptive aphasia)
• Nominal aphasia (anomic aphasia)
• Global aphasia
• Conduction aphasia
• Transcortical motor aphasia
• Transcortical sensory aphasia
• Mixed transcortical aphasia

The following table summarizes some major characteristics of different types of aphasia:

This article is licensed under the GNU Free Documentation License.
It uses material from the Wikipedia article "Metasyntactic variable".