蝸電図よりみた脳血管障害による内耳障害の病態

PATHOPHYSIOLOGY OF INNER EAR DISORDERS CAUSED BY CEREBRAL VASCULAR LESIONS DEDUCED BY ELECTROCOCHLEOGRAPHY

　脳腫瘍や脳血管障害などの頭蓋内疾患によつて聴覚系もしばしば障害されるが，とくに後頭蓋窩の疾患では脳幹はもとより，障害の部位によつては内耳も何らかの影響をうけると思われる。

　最近，頭蓋内疾患に対して従来の聴覚心理学的方法による聴力検査に加えて，他覚的聴力検査（auditory evoked potential^1））によつて，病巣局在診断や聴覚系の機能を客観的に把握しようとする試みがなされてきている。

　Electrocochleography was performed in three cases with perceptive hearing loss caused by cerebral vascular lesions. Recording was made with use of the transtympanic needle electrode technique.

　In a case of aneurysm of the anterior inferior cerebellar artery with fluctuate hearing loss, decay of the action potential (AP) was more pronouncedthan that of the cochlear microphonics (CM), but the summating potential (SP) maintained a comparably stable potential. These electrocochleo - graphic findings seemed to suggest that the cochlear nerve would be more affected than the cochlear hair cells in the damage of both cochlear nerve and hair cells, and the existence of some kind of sensory cells which were inde-structible even despite the obstacle of the inner ear blood flow.

　Concerning the electrocochleography, it was conjectured that the cochleas of the cases showing normal CM and SP responses were hardly affected even though these pure tone audiometries indicated profound perceptive hearing loss caused by cerebral vascular lesions, and furthermore, in some cases with no AP and CM responses after long lapse these cochleas were damaged irreversibly and organically.