Sacral spinal dural arteriovenous fistula: diagnostic pitfalls and treatment challenges. Illustrative case

BACKGROUND: Sacral spinal dural arteriovenous fistulas (sDAVFs) are rare and easily missed on imaging, especially when supplied by internal iliac branches. Regional vascular anatomy may complicate endovascular treatment approaches. OBSERVATIONS: A 71-year-old man with symptoms suggestive of spinal myelopathy underwent spinal MRI, which revealed multisegment T2 cord hyperintensity from T7 to L1 without serpiginous flow voids; spinal MR angiography (MRA) findings were negative for sDAVF. On spinal digital subtraction angiography (DSA), selective internal iliac injection identified a right S1 sDAVF originating from a lateral sacral artery branch. Transarterial Onyx embolization formed a plug proximal to the fistula, resulting in failed obliteration. Subsequent microsurgical disconnection via S1 laminectomy appeared successful on intraoperative ICG angiography, but postoperative angiography revealed residual shunting. Reexploration with L5 laminectomy allowed definitive microsurgical ligation, resulting in lasting cure at the 1-year follow-up. LESSONS: Negative spinal MRI/MRA findings do not rule out sacral sDAVF; complete spinal DSA, including internal iliac injection, is critical if sacral sDAVF is suspected. Sacral angioarchitecture may hinder durable embolization, warranting consideration of upfront microsurgical ligation. With ligation, intraoperative ICG angiography may miss residual flow; immediate postoperative angiography should be best practice. With microsurgical ligation, broad exposures may be ideal for identifying all arterialized veins. https://thejns.org/doi/10.3171/CASE26220.