What is aphasia, the brain condition sidelining Bruce Willis?

The announcement by American actor Bruce Willis that he will be "stepping away" from the big screen has drawn attention to aphasia, a little-known condition with many causes. Willis's family said on Wednesday he had recently been diagnosed with the condition, which they said is "impacting his cognitive abilities". "As a result of this and with much consideration, Bruce is stepping away from the career that has meant so much to him," the family said in a statement. The cause of the 67-year-old's condition was not revealed. Aphasia can affect the ability to produce and comprehend both written and spoken communication.