Histopathological aspects of dural arteriovenous fistulas in the transverse-sigmoid sinus region in nine patients

OBJECTIVE: In recent years, dural arteriovenous fistulas (DAVFs) have been primarily thought to be acquired lesions, formed after sinus thrombosis. The pathogenesis of DAVF, however, is still controversial. We have studied histopathological aspects of DAVFs in resected specimens obtained from nine patients, to obtain clues to the pathogenesis of DAVFs. METHODS: Histological comparison was made among nine DAVF cases and five control cases without venous sinus disease. In addition, the relationship between the clinical course and histological aspects was investigated. RESULTS: The essential abnormality found was a connection between the dural arteries and the dural veins within the venous sinus wall, through small vessels averaging approximately 30 μm in diameter. By using several staining methods, we confirmed that the vessels were part of the venous system; we named these dilated venules 'crack-like vessels.' CONCLUSION: The development of abnormal communications between dural arteries and dural veins (crack-like vessels) is regarded as the essential part of the pathogenesis of DAVFs, and sinus thrombus is not thought to be an essential lesion of DAVEs. It might be postulated that sinus hypertension caused by stenocclusive disease of the venous sinuses triggers the development of fistulous connections between arteries and veins in the dural wall, which may result in increasingly dilated venules and the formation of DAVFs.