Aphasia is an acquired language disorder caused by damage to the brain. This class of language disorder ranges from having difficulty remembering words to losing the ability to speak, read, or write, but does not affect intelligence. This also affects visual language such as sign language. Aphasia is usually caused by brain damage, most commonly caused by stroke. Brain damage linked to aphasia can also be caused by other brain diseases, including cancer, epilepsy, and Alzheimer's disease. Acute aphasia disorders usually develop quickly as a result of head injury or stroke, and progressive forms of aphasia develop slowly from a brain tumor, infection, or dementia. The area and extent of brain damage or atrophy will determine the type of aphasia and its symptoms. Aphasia types include expressive aphasia, receptive aphasia, conduction aphasia, anomic aphasia, global aphasia, primary progressive aphasias and many others. Medical evaluations for the disorder range from clinical screenings by a neurologist to extensive tests by a speech-language pathologist or neuropsychologist. Most acute aphasia patients can recover some or most skills by working with a speech-language pathologist.