脳静脈血行障害時の脳循環動態と病理学的変化に関する研究

Abstract

In cerebral circulation, there are many detailed reports of arterial circulatory disturbance but few reports of venous circulatory disturbance. In Experiment Ⅰ, regional cerebral blood flow (rCBF) and intracranial pressure (ICP) response to transient superior sagittal sinus (SSS) occlusion were measured in twenty-one anesthetized cats. Cats were divided into three groups according to the duration of SSS occlusion (1, 3, 6 hours). Irreversible changes, such as no recovery of rCBF, thrombosed parenchymal vessel, and loss of nouronal cell, were observed in groups with more than 3 hours' occlusion. Consequently it was suspected that the time limit of transient cerebral venous occlusion was 3 hours. In Experiment Ⅱ, diameter of pial vessels and ICP response to complete cerebral venous occlusion were measured continuously in thirty anesthetized cats. 0.3 ml of cyanoacrylate were injected into anterior SSS to occlude the SSS and cortical veins. Six hours after injection the state of blood-brain-barrier disruption and pathological changes were evaluated. As for the response of pial arterioles in early stages, 2-24% contraction of arteriole was observed in fifteen cats and 2-16% dilatation was observed in six cats. In later stages, 1-87% dilatation of arteriole was observed in ten cats. The elevation of ICP and dilatation of arteriole were observed in the same period. Pathologically intracerebral hematoma (ICH) was observed in eight cats. These were all in the white matter of suprasylvian gyrus. In all ICH cases, two marginal veins surrounding the gyrus were occluded by cyanoacrylate. The dominant mechanism of CBF control is metabolic, not myogenic. According to this theory, the contraction of arteriole cannot be explained. This suggests that pial arterioles contract on very high venous pressure (transmural pressure). Consequently it was suspected that with very high venous pressure, more than 30-100 mmHg, the dominant mechanism is myogenic. Occlusion of adjoining two marginal veins causes severe circulatory disturbance such as brain swelling and ICH.