Spontaneous Superior Ophthalmic Vein Thrombosis Resulted in Posterior Fossa Venous Congestion in a Case of Cavernous Sinus Dural Arteriovenous Fistula: Successful Treatment with Direct Interruption Surgery.

Cavernous sinus dural arteriovenous fistulas are generally considered to have a benign clinical course, as spontaneous thrombosis of the fistula or draining veins can result in regression of the lesion. However, we encountered a rare case in which this hemodynamic change led to rapid neurological deterioration, necessitating microsurgical intervention. A 72-year-old woman presenting with chemosis and exophthalmos was diagnosed with a cavernous sinus dural arteriovenous fistula. Cerebral angiography revealed 2 venous drainage routes: the superior ophthalmic vein anteriorly and the superior petrosal sinus towards the petrosal vein posteriorly. Approximately 2 weeks after diagnosis, while awaiting elective endovascular treatment, the patient developed spontaneous thrombosis of the superior ophthalmic vein. This redirected shunt flow exclusively into the petrosal vein, leading to venous congestion in the posterior fossa. Consequently, the patient experienced rapid neurological deterioration accompanied by brain edema in the cerebellum and brainstem. Furthermore, the loss of transvenous access rendered curative endovascular treatment unfeasible. The patient was therefore treated with urgent microsurgical interruption of the petrosal vein via a retrosigmoid approach. This resulted in complete neurological recovery and angiographic obliteration of the cavernous sinus dural arteriovenous fistulas. This case highlights the importance of close observation while waiting for the intervention for cavernous sinus dural arteriovenous fistulas with cortical venous reflux, given the risk of spontaneous hemodynamic change. It also underscores the role of microsurgical intervention as a salvage option when endovascular treatment becomes unfeasible.