Interhemispheric suppression: a test of central auditory function.

Two groups of brain damaged adults, those with cerebrocranial injury (CCI) and victims of cerebrovascular accident (CVA) were tested with the competing sentences test of Willeford (In: Central Auditory Dysfunction. New York: Grune and Stratton, 1977: Chap 2). The main purpose was the exposure of functional disorders of communication in such patients who test within normal or near-normal limits on routine audiological testing and also on tests for aphasia. Of 142 serially admitted CCI patients, 43%, many with diffuse lesions, gave abnormal responses, mostly at the left ear, with 19 of them showing total extinction at that ear. On two sound field competing message tests the CCI patients were significantly poorer than normal controls. CVA patients with confirmed right hemisphere lesions tended strongly toward left ear suppression, while left hemisphere damaged patients often showed bilateral drop in scores. It is clear that brain damaged patients can have central dysfunction of auditory processing despite normal findings on routine audiological tests and tests for aphasia. The implications for activities of daily living and for habilitation are discussed.