Surgical ligation of filum terminale type IV arteriovenous fistula with giant venous varix.

The authors present the case of a type IVc filum terminale arteriovenous fistula in a female patient in her 40s, who presented with lower abdominal pain, back pain, and lower extremity weakness. MRI showed an intradural mass with serpiginous vessels. Spinal angiography revealed a type IVc perimedullary fistula primarily fed by the anterior spinal artery with a giant venous varix. Because of anatomical factors, endovascular embolization was not feasible, and surgical ligation was performed via laminectomy at L1-3. The fistula seen within the filum terminale was successfully clipped, with no further venous outflow on angiography. The patient recovered with complete symptom improvement. The video can be found here: https://stream.cadmore.media/r10.3171/2025.7.FOCVID2536.