T entorial dural arteriovenous fistulae (DAVF) are rare and dangerous lesions (2, 3, 5, 14, 15, 24, 31). In a meta-analy- sis of 377 patients with DAVF reported before 1989, ten- torial DAVF were less common than transverse-sigmoid sinus and cavernous sinus DAVF (8 versus 63 and 12%, respectively), but tentorial DAVF had the most aggressive neurological behavior, with 97% causing hemorrhage or progressive focal neurological deficits (2). Tentorial DAVF frequently have angio- graphic features associated with hemorrhage: retrograde drainage through cortical or subarachnoid veins, deep drainage through the vein of Galen, and venous varices. Consequently, tentorial DAVF are treated aggressively when diagnosed, even in the absence of presenting hemorrhage (24). Endovascular therapy has become the predominant therapy for intracranial DAVF because their arterial supply from the external carotid artery (ECA) can be embolized safely, and their location on dural venous sinuses facilitates access and occlu- sion through that sinus (1, 9, 10, 24, 26, 31). The combination of transarterial and transvenous embolization results in high obliteration rates for most DAVF, but tentorial DAVF are an exception. Their arterial supply is extensive, involving meningeal arteries from the internal carotid artery (ICA) and vertebral artery that are difficult to cannulate and riskier to embolize than ECA feeders. Transvenous navigation to deeper locations around the tentorium is difficult. More importantly, tentorial DAVF often drain exclusively to subarachnoid veins rather than to their associated sinus (Borden Type III), which prevents transvenous access (3). Therefore, the management of tentorial DAVF may require microsurgical interruption, unlike most other DAVF (6, 8, 10, 12–14, 23, 26, 30). ONS110 | VOLUME 62 | OPERATIVE NEUROSURGERY 1 | MARCH 2008 www.neurosurgery-online.com Surgical Anatomy and Technique Michael T. Lawton, M.D. Department of Neurological Surgery, University of California, San Francisco, San Francisco, California Rene O. Sanchez-Mejia, M.D. Department of Neurological Surgery, University of California, San Francisco, San Francisco, California Diep Pham, B.A. Department of Neurological Surgery, University of California, San Francisco, San Francisco, California Jeffrey Tan, B.A. Department of Neurological Surgery, University of California, San Francisco, San Francisco, California Van V. Halbach, M.D. Department of Interventional Neuroradiology, University of California, San Francisco San Francisco, California Reprint requests: Michael T. Lawton, M.D., 505 Parnassus Avenue, M-780C, San Francisco, CA 94143–0112. Email: lawtonm@neurosurg.ucsf.edu Received, March 29, 2007. Accepted, July 31, 2007. VASCULAR TENTORIAL DURAL ARTERIOVENOUS FISTULAE: OPERATIVE STRATEGIES AND MICROSURGICAL RESULTS FOR SIX TYPES OBJECTIVE: Tentorial dural arteriovenous fistulae (DAVF) are rare, have a high risk of hemorrhage, often cannot be obliterated endovascularly, and frequently require micro- surgical interruption of the draining vein. We differentiated these fistulae into six types and developed specific operative strategies on the basis of these types. METHODS: During a 9-year period, 31 patients underwent microsurgical treatment for tentorial fistulae: seven galenic DAVF, eight straight sinus DAVF, three torcular DAVF, three tentorial sinus DAVF, eight superior petrosal sinus DAVF, and two incisural DAVF. RESULTS: The posterior interhemispheric approach was used with galenic DAVF; the supracerebellar-infratentorial approach was used with straight sinus DAVF; a torcular craniotomy was used with torcular DAVF; the supratentorial-infraoccipital approach was used with tentorial sinus DAVF; the extended retrosigmoid approach was used with superior petrosal sinus DAVF; and a pterional or subtemporal approach was used with incisural DAVF. Angiographically, 94% of the fistulae were obliterated completely. Four patients had transient neurological morbidity, none had permanent neurological mor- bidity; and there was no operative mortality (mean follow-up, 4.2 yr). CONCLUSION: Tentorial DAVF can be differentiated on the basis of fistula location, dural base, associated sinus, and direction of venous drainage. The operative strategy for each type is almost algorithmic, with each type having an optimum surgical approach and an optimum patient position that allows gravity to retract the brain, open subarachnoid planes, and shorten dissection times. No matter the type, the fistula is treated microsur- gically by simple interruption of the draining vein. KEY WORDS: Arteriovenous malformation, Dural arteriovenous fistula, Microsurgery, Operative approaches, Tentorium Neurosurgery 62:ONS110-ONS125, 2008 DOI: 10.1227/01.NEU.0000297027.98243.21