[Multiple dural arteriovenous fistulas involving both the cavernous sinus and the posterior fossa: report of two cases and review of the literature].

Multiple dural arteriovenous fistulas (DAVFs) are rare, accounting for 7% of all intracranial DAVFs. The authors describe two cases of multiple DAVFs involving both the cavernous sinus and the posterior fossa. The first patient was a 45-year-old man who presented with visual disturbance, chemosis, exophthalmus, and tinnitus. Angiograms demonstrated DAVFs involving the right cavernous sinus and the ipsilateral sigmoid sinus. Soon after transarterial embolization via the right occipital artery, the patient's symptoms completely disappeared. Six months later, follow-up angiograms showed disappearance of the cavernous DAVF and a subtle opacification of the sigmoid sinus DAVF. The patient has been free from symptoms for four years. The second patient was a 75-year-old woman who presented with progressive tinnitus two years after stereotactic radiosurgery for right cavernous DAVF. Angiograms showed a new lesion in the contralateral transverse and sigmoid sinuses. Transvenous embolization (TVE) of the affected sinuses was successful and the patient's symptoms disappeared. The patient's course has been uneventful after treatment, and follow-up MR angiograms have not shown any recurrence of lesions. To our knowledge, 25 cases of multiple DAVFs have been reported in the literature, of which we reviewed 12 cases of multiple DAVFs affecting the cavernous sinus. The patients' ages ranged from 43 to 75 years with a mean of 57.4 and their distribution showed female predominance. Other DAVFs occurred mostly in the transverse and sigmoid sinuses. With the exception of our case (second patient), the posterior fossa lesions were located on the same side as the cavernous sinus DAVF. Multiple DAVFs were detected simultaneously in 5 of the 12 cases with the initial angiograms. In the other 7 cases, cavernous DAVFs had been treated, but were followed by posterior fossa lesions occurring after various intervals (4 months to 2.5 years). All the patients presented with ocular signs due to cavernous DAVFs. Based upon our review of the literature, we discuss here three possible hypotheses. The first possibility for formation of multiple DAVFs concerns their primary etiology, viz. that they develop after a huge sinus thrombosis involving several sinuses and its recanalization. A second possibility is the secondary formation of DAVFs. Preexisting cavernous sinus DAVFs induce sinus thrombosis and/or venous hypertension, which results in the formation of multiple lesions. A third possibility is that they are due to other factors, including increased angiogenic activity and some technical problems associated with TVE. Our review indicates that careful follow-up for several years should be made after treatment of cavernous DAVFs.