What is aphasia? Cognitive disease Bruce Willis was diagnosed with can leave a person unable to communicate

On Wednesday, the family of action star Bruce Willis announced that the actor has been diagnosed with aphasia, causing him to step away from his career at the age of 67.  Aphasia is cognitive medical condition that leaves patients struggling to understand language and communicate. 

According to Mayo Clinic, aphasia can begin as trouble communicating. Someone with aphasia might have trouble finding the correct words, substitute the wrong words for each other or speak in short sentences that are difficult or impossible to understand. These issues are related to brain damage in the left side of the brain, which controls language, Johns Hopkins explains.

While its presentations can vary, aphasia is usually a symptom of a broader medical issue. It may result from a stroke, head injury or tumor, or develop due to a degenerative brain condition.