De novo formation of orbital cavernous malformation 9 years after surgical management of dural arteriovenous fistula in the anterior middle fossa

A 30-year-old man presented with recurrent dural arteriovenous fistula (dAVF) associated with de novo orbital cavernous malformation (CM), manifesting as progressive left visual disturbance. He had undergone transarterial embolization and subsequent surgical management for a left anterior middle fossa dAVF 9 years previously. External carotid angiography showed recurrence of the dAVF. Magnetic resonance imaging revealed a well delineated intraorbital mass lesion with hypointense signal rim by T₂-weighted imaging, adjacent to the shunting point of the recurrent dAVF. Transcranial subtotal removal of the intraorbital mass lesion through the orbitopterional approach revealed continuity between the mass lesion and the draining vein of the recurrent dAVF. The histological diagnosis was CM. His symptom was relieved postoperatively, and no regrowth was seen during the follow-up period of one year. The coexistence of recurrent dAVF with newly formed orbital CM is extremely rare, but may indicate the underlying mechanism of the formation of CMs and recurrent dAVF.