Aphasia

Aphasia, also known as dysphasia, is an impairment in a person's ability to comprehend or formulate language because of dysfunction in specific brain regions. The major causes are stroke and head trauma; prevalence is hard to determine, but aphasia due to stroke is estimated to be 0.1–0.4% in developed countries. Aphasia can also be the result of brain tumors, epilepsy, autoimmune neurological diseases like multiple sclerosis, infection of the brain, or neurodegenerative diseases like dementias.

To be diagnosed with aphasia, a person's ability to produce and/or comprehend written and/or spoken language must be significantly impaired. In the case of progressive aphasia, this impairment progresses slowly with time.

The difficulties of people with aphasia can range from occasional trouble finding words, to losing the ability to speak, read, or write; intelligence, however, is unaffected. Expressive language and receptive language can both be affected as well. Aphasia also affects visual language such as sign language. In contrast, the use of formulaic expressions in everyday communication is often preserved. For example, while a person with aphasia, particularly expressive aphasia (Broca's aphasia), may not be able to ask a loved one when their birthday is, they may still be able to sing "Happy Birthday". One prevalent deficit in all aphasias is anomia, in which the affected individual has difficulty finding the correct word.