‘SO-CALLED’ CORTICAL DEAFNESS

Abstract

Two patients with severe, persistent hearing loss caused by bilateral cerebral lesions are described. To determine the location of lesions responsible for the severe hearing loss, we examined magnetic resonance images and compared the lesions in these 2 patients with those in another with only mild hearing loss following extensive bilateral temporoparietal lesions. The extent of bilateral damage to the white matter adjacent to the posterior half of the putamen proved crucial in determining the severity of the hearing loss. Hearing loss was more severe when the white matter immediately ventral and lateral to the posterior half of the putamen was involved bilaterally. Based on this observation and from a review of the literature, we infer that the auditory radiations in humans course in a dense tract from the medial geniculate body up to the sublenticular region, and disperse from there to the primary auditory cortex as well as to the other auditory-related areas, partly by coursing through the white matter immediately ventral to the posterior half of the putamen, and partly by penetrating the ventral and lateral portions of the posterior half of the putamen. Accordingly, bilateral lesions in the white matter ventral and lateral to the posterior half of the putamen appear to interrupt all the projection fibres from the medial geniculate bodies to the auditory-related areas, resulting in severe, persistent hearing loss.