Consideration for cerebral AVMs from the histological study on perinidal vascular structures

In order to elucidate the pathophysiology of cerebral arteriovenous malformations (AVMs), 21 resected specimens are examined pathologically on vascular structure in the brain adjacent to the nidus. In serial sections, dilated capillary vessels were observed in all cases. They existed in the brain within 1-7 mm from the boundary of the nidus. Three-dimensional reconstruction of the vessels revealed perinidal dilated capillary network (PDCN) in all specimens. PDCN connected with not only the nidus, feeding artery, draining vein, but also the normal capillary, arteriole and venule. PDCN is extremely dilated (10-30 times) capillary network and already losing the regulating function of blood flow due to stasis. That is, hemodynamics in PDCN is almost the same as that of AVM nidus. From these findings, our consideration for cerebral AVMs concerning the surgical procedure, the postoperative bleeding and the mechanism of nidus enlargement will be discussed.