前下小脳動脈循環障害と平衡覚・聴覚機能に関する実験的研究

Abstract

Regional brainstem blood flow and brainstem functions were measured after permanent unilateral anterior inferior cerebellar artery (AICA) occlusion in the rat brainstem using an autoradiographic technique, Laser-Doppler method, Caloric test and auditory brainstem response (ABR). Morphological ischemic changes were assessed using immunohistochemical observation. The results were as follows : 1. Two hours after occlusion of the unilateral AICA, blood flow in the ipsilateral vestibular nucleus (VN) revealed a 75% recovery, while the blood flow in the ipsilateral cochlear nucleus (CN) recovered to the control level. The increase in the blood flow from the collateral circulation was measured by the Laser-Doppler method when the unilateral AICA was occluded. The increase rate of blood flow in the brainstem showed a maximal increase of 33%. 2. It was possible to assess brainstem function using ABR. Three types of ABR waves were classified when the unilateral AICA was occluded. It was thought that all components re-appeared in type 2 because the cochlear blood flow was re-established quickly by collateral circulation. Even in contralateral recording of ABR, dysfunction of the brainstem was observed. The characteristic findings included a signigicant increase in the inter-peak latency between components Ⅰ-Ⅳ and Ⅱb-Ⅳ. 3. From immunohistochemical observation using Microtubule-associated protein 2 (MAP 2), ischemic lesions were clearly detected as a loss of reaction in the nerve cell bodies, dendrites and neuropils in the unilateral VN and CN. The changes two hours after occlusion of the ipsilateral AICA were more comprehensive than those thirty minutes after occlusion. 4. From our findings, a discrepancy in recovery between blood flow and function in the brainstem is indicated.