HISTOPATHOLOGICAL ASPECTS OF DURAL ARTERIOVENOUS-FISTULAS IN THE TRANSVERSE-SIGMOID SINUS REGION IN 9 PATIENTS

OBJECTIVE: In recent years, dural arteriovenous fistulas (DAVFs) have been primarily thought to be acquired lesions, formed after sinus thro mbosis. 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 DA VFs. METHODS: Histological comparison was made among nine DAVF cases a nd five control cases without venous sinus disease. In addition, the r elationship between the clinical course and histological aspects was i nvestigated. RESULTS: The essential abnormality found was a connection between the dural arteries and the dural veins within the venous sinu s wall, through small vessels averaging approximately 30 mu m in diame ter. 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 communication s between dural arteries and dural veins (crack-like vessels) is regar ded as the essential part of the pathogenesis of DAVFs, and sinus thro mbus is not thought to be an essential lesion of DAVFs. It might be po stulated that sinus hypertension caused by stenocclusive disease of th e venous sinuses triggers the development of fistulous connections bet ween arteries and veins in the dural wall, which may result in increas ingly dilated venules and the formation of DAVFs.