High-cervical Perimedullary Arteriovenous Fistula at C2: Staged Posterior Flow Control Followed by Transoral Direct Obliteration with Long-term Independence

Perimedullary arteriovenous fistulas at the craniocervical junction are rare, frequently present with subarachnoid hemorrhage, and require accurate identification of the shunt point―particularly in lesions involving the anterior spinal artery―to achieve durable cure. A 64-year-old man presented with dense posterior fossa subarachnoid hemorrhage caused by a high-flow craniocervical junction arteriovenous shunt supplied predominantly by a markedly enlarged right C2 radiculomedullary artery. Selective catheterization was unsuccessful. On day 1, suboccipital craniectomy with C1 laminectomy enabled posterior flow control by clipping the dominant feeder; however, the ventral shunt point could not be safely visualized. Postoperative angiography demonstrated persistent shunting with prominent anterior spinal artery contribution. One month later, definitive transoral anterior obliteration was performed in a hybrid operating room. Intraoperative digital subtraction angiography and intra-arterial indocyanine green angiography demonstrated caudal-to-rostral flow reversal from the anterior spinal artery into the ascending anterior spinal vein at the shunt point, located within the anterior median fissure on the ventral pial surface. The shunt was directly obliterated by simultaneous clipping of the anterior spinal artery branch and draining vein, with additional coagulation of minor feeders. Halo immobilization followed by delayed posterior C1-2 fixation was performed. Final angiography and serial magnetic resonance angiography confirmed complete cure, and the patient returned to work 10 months postoperatively, maintaining functional independence for more than 5 years. This case illustrates that, in carefully selected anterior spinal artery-involved high-flow craniocervical junction perimedullary arteriovenous fistulas, a staged strategy combining posterior flow control and definitive anterior direct obliteration can provide a safe and durable solution.