Question:
Perhaps some med student could give a definitive description butthis is what I heard:

Aphasia is a condition that is usually brought about by a blow to thehead. It results in a person being unable to combine words to makesentences. The victim does think he/she is making sense and getsrather annoyed when people don't understand him/her.

What I don't know is whether or not victims understand what othersare saying.I think they would because the problem is related to their ability tocombine words to make sentences and not their ability to decifer whatsomeone else says ... but I can't say for sure.

Answer: Actually aphasia can be caused by any traumatic brain injury, althoughit is typically caused by stroke (occlusion of one of the main brainarteries). There are several types of aphasia (six categories in mostbooks), so which one a patient has depends on the location of thebrain damage. Typically this damage is in the left hemisphere. If thedamage is restricted to the lower secondary motor cortex (Broca's Area),the patient usually suffers Broca's aphasia: patient has difficultycontroling motor output of their speech, but is aware that he cannotsay what he wants. If the damage is in upper secondary temporal cortex(Wernicke's Area), the patient usually suffers Wernicke's aphasia:patient has fluent speech (well-spoken mechanically) that make's littlesense, and he is not aware of his deficit. There are four otheraphasia types: two type of transcortical aphasias, global aphasia, andconduction aphasia. Each has a different, typical location of the braindamage (e.g., conduction aphasiacs usually have damage in the arcuatefasciculus, a bunch of fibers connecting Broca's and Wernicke's Areas),and a different set of clinical behavior patterns. In testing,repition of speech, fluency, and comprehension are used to judge thecondition (as well as a variety of standardized tests). Please notthat the different categories of aphasias overlap tremendously andare still subject to some controversy as to whether or not theyconstitute a separate condition. In addition, patients may havethe a particular category's behavior type but brain damage in a differentarea.