椎骨脳底動脈循環障害とめまいの病態生理の理解のために3.実験的椎骨脳底動脈循環障害時の機能検査

温度刺激検査,蝸電図,ABR

抄録

Using the rats with ischemia induced by occlusion of the anterior inferior cerebellar artery (AICA) or vertebral artery (VA), we investigated the auditory brainstem response (ABR), electrocochleogram and caloric tests. Upon occlusion of the VA, there was no change in the ABR, whereas in the caloric test the duration of nystagmus on stimulating both ears shortened. After occlusion of the AICA, ABRs were classified into three patterns: all components disappeared: n=4; all components disappeared transiently and then recovered: n=2; the interpeak latency between I and IV wave increased: n=7. Upon occlusion of the AICA, the cochlear blood flow (CoBF) showed one of three pat-terns of change: no change: n=5; decrease: n=10; and transient decrease with recovery: n=5. The cochlear potentials were dependent on residual CoBF. In the caloric test, when the left AICA was occluded, the duration of nystagmus induced by stimulation of the left (ipsilateral) ear was shorter than that induced by the right (contralateral) ear. Based on the functional test results, we conclude that in this model of ischemia the function of the vestibular system including the semicircular canal is more severely affected than the hearing function.