word deafness

n. Neuropsychological syndrome characterized by severe difficulties in understanding spoken language, with sparing written language understanding and language production. Patients who have this disorder can hear, but they cannot discriminate the language sounds (phonemes). When a clear and overt dissociation between oral and written language understanding is observed, frequently the term pure word deafness is used. Because of the preserved ability to understand written language, it can be interpreted as an auditory processing defect (verbal auditory agnosia). Word deafness has been regarded either as a subtype of Wernicke's aphasia, as an independent aphasic disorder, or just as one of the underlying disturbances in Wernicke's aphasia. Some phoneme discrimination defects are usually found in cases of Wernicke's aphasia and left temporal lobe damage, but cases of pure word deafness are extremely unusual. Reported cases have found a left or bilateral superior temporal lobe pathology including the Heschl's gyrus or the auditory projection to this region. Word deafness is most frequently caused by cerebrovascular accidents or head injuries, with left or bitemporal cortico-subcortical lesions. Although it is assumed that the auditory recognition defect is limited to language, testing of nonlinguistic sound comprehension and music usually has found a more pervasive auditory agnosia. In cases of unilateral pathology, significant recovery has been observed over time. – AA