Sphenoidal diploic arteriovenous fistula with cortical venous reflux: A case report

Background: Sphenoidal diploic arteriovenous fistulas (AVFs) are exceptionally rare. When accompanied by cortical venous reflux (CVR), they are considered high-risk lesions with a potential for intracranial hemorrhage, warranting prompt treatment. Endovascular management is challenging in the sphenoidal region because arterial feeders often harbor extracranial-intracranial anastomoses. Case Description: A 67-year-old woman presented with chronic left temporal headache and tinnitus. Cerebral angiography revealed a sphenoidal diploic AVF with CVR. The shunt was located in the lateral sphenoid diploe and was supplied by branches of the external carotid system, including the anterior deep temporal artery and the middle meningeal artery. Venous drainage occurred through an ascending diploic vein into a parasagittal meningeal sinus (venous lacuna) with reflux into an adjacent cortical vein. The lesion was treated by transarterial Onyx embolization with balloon assistance for flow control. Careful feeder selection was essential to avoid high-risk anastomoses, particularly meningo-ophthalmic connections. Complete angiographic obliteration was achieved without complications, with immediate symptom resolution. No recurrence was observed during 4 years of follow-up. Conclusion: Transarterial Onyx embolization with appropriate flow-control techniques can be a safe and effective option for sphenoidal diploic AVFs with CVR. This case underscores that the presence of CVR itself is the key indication for treatment, irrespective of whether the venous reflux pathway is direct or indirect, and that meticulous angiographic assessment and feeder selection are critical for procedural safety.