Aphasia

Aphasia (or aphemia) is a loss of the ability to produce and/or comprehend language, due to injury to brain areas specialized for these functions. It is not a result of deafness or muscle paralysis, and it does not necessarily affect intelligence. Aphasia can be distinguished from dysphasia, the prefix a- indicating a complete loss, which is a condition usually only seen in adult brain damage, when it is too late in life for the nervous system to make gross adjustments. In contrast, the prefix dys- indicates a partial loss, which is more common when the dysfunction occurs in children.

Depending on the area and extent of the damage, someone suffering from aphasia may be able to speak but not write, or vice versa, or display any of a wide variety of other deficiencies in language comprehension and production. Aphasia may co-occur with speech disorders such as dysarthria or apraxia of speech, which also result from brain damage.