Impairment in the use of spoken or written language caused by injury to the brain, which cannot be accounted for by paralysis or incoordination of the articulatory organs, impairment of hearing or vision, impaired level of consciousness, or impaired motivation to communicate. The language zone in the brain includes the portion of the frontal, temporal, and parietal lobes surrounding the sylvian fissure and structures deep to these areas. In right-handed persons, with few exceptions, only injury in the left cerebral hemisphere produces aphasia. Lateralization of language function is variable in left-handers, and they are at greater risk for becoming aphasic from a lesion in either hemisphere.