Abrupt unilateral deafness modifies function of human auditory pathways.

We studied nine patients with unilateral abrupt deafness caused by acoustic neuroma surgery. Cortical responses to tones delivered to the intact ear were recorded postoperatively with a 122-channel whole-scalp neuromagnetometer. In three patients, followed for 12 months with 2-4 measurements, evoked responses originating in the auditory cortices were weak and delayed one month after the operation in both hemispheres. During the follow-up, the amplitudes reached the control level. No response abnormalities were found in patients who were studied 1.5-4.5 years after the operation. Our findings suggest that abrupt unilateral deafness causes immediate changes in the function of auditory pathways of adult humans and that reorganization takes place within 1 year.