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