Aphasia is a disorder that results from damage to the language areas of the brain.

A person with aphasia may experience difficulties with speaking, understanding, reading and/or writing.

Aphasia is often caused by stroke but any disease or damage to the brain parts t​hat control language can give rise to aphasia. This includes traumatic brain injury, dementia and brain tumours. For most people, the language areas are located in the left side of the brain. Therefore, left brain damage can cause a person to suffer from aphasia.

What are the signs and symptoms of aphasia?

​Some people with aphasia have receptive aphasia, which means they have problem understanding what is said. Some may have expressive aphasia, which is difficulty expressing oneself using words. Others may have both receptive and expressive aphasia.

Aphasia can also cause problems with written language. Aphasia may lead to difficulties with reading and writing in people who were literate before the brain damage.

The severity of the aphasia depends on the extent and area of damage to the brain. Persons with mild aphasia may be able to partake in day-to-day conversations fairly well but may have difficulties understanding complex instructions. They may also experience some trouble in expressing their thoughts fluently due to difficulty "finding the right words" to use.

In contrast, people with severe aphasia may not understand anything that is said to them. They may be unable to say anything, or if they attempt a few words, those words may be repeated again and again (a phenomenon called perseveration) in all responses. In other cases, a person with severe aphasia may appear to be speaking fluently, but most of the words and sentences do not make sense.

For information on how asphasia is diagnosed and treated​, see next page.​​