One Million With Acquired Aphasia in U.S. It has been estimated that about one million people in the United States have acquired aphasia. Aphasia is an impairment of the ability to use or comprehend words, usually acquired as a result of a stroke or other brain injury. There are several different types of aphasia depending on the location of the brain injury. There is currently no drug treatment for aphasia although surgery and speech therapy are sometimes successfully used as treatment.