Aphasia is an acquired language disorder caused by damage to the brain, most often after a stroke affecting the left hemisphere language areas. It can also follow a traumatic brain injury, a brain tumour or surgery to remove one, or the neurodegenerative condition known as primary progressive aphasia (PPA), a form of frontotemporal dementia.
Aphasia can affect any part of language - speaking, understanding, reading and writing - and it affects people very differently. Some people know exactly what they want to say and cannot get the words out. Others speak fluently but the words that come out are not the ones they intended. Many struggle to follow fast conversation, or find long paragraphs of writing hard to hold onto.
It is important to distinguish aphasia from two other conditions it is often confused with. Dysarthria is a motor speech disorder - the muscles that produce speech are weak or uncoordinated, but language itself is preserved. Cognitive-communication difficulty is a change in the thinking that surrounds language - attention, memory and social judgement - rather than in the language system itself. A specialist speech and language therapy assessment separates them and points the therapy plan in the right direction.
Aphasia is common. Around a third of people who have a stroke develop some form of aphasia. With the right therapy, delivered at the right intensity, and with family and friends learning to support conversation, meaningful language recovery is possible for many years after the injury.