Abnormal auditory neural networks in patients with right hemispheric infarction, chronic dizziness, and moyamoya disease: a magnetoencephalogram study.

The purpose of this study was to determine whether the auditory cortex is sensitive to cortical insults and to determine the specificity of the insults in three clinical situations with different cortical involvement. Auditory-evoked magnetic fields of ten normal subjects, 8 patients with right hemispheric infarction, 11 with chronic dizziness, and 2 with moyamoya disease were measured. To analyze the abnormality of auditory neural networks, the magnitude ratio and the angle difference (Deltatheta) between response vectors, which were determined from maximum current arrows corresponding to the N100m peak for contralateral and ipsilateral stimuli were used. A normal range of the parameters was defined so that abnormal values could be determined. Of the three parameters, Deltatheta was the most sensitive: 4 patients with right hemispheric infarction, 4 with chronic dizziness, and 1 with moyamoya disease had abnormal Deltatheta. The electrical activity in the patients with such abnormal Deltathetas had a circular current pattern. These findings suggest that right infarction lesions sometime affect the left auditory neural network, dizziness is caused by abnormal neural networks between the vestibular cortical area and the auditory cortex or by an imbalance between left and right auditory-cortex activities, and moyamoya-disease patients have almost normal auditory-electrical activity.