Sacral arteriovenous fistula with lower thoracic cord edema without perimedullary vein enlargement

Abstract

Background: Sacral dural arteriovenous fistulas (AVFs) are often undiagnosed at the initial presentation due to their rarity.

Case description: For 1 year, a 71-year-old man developed progressive motor and sensory disturbances in both legs. Magnetic resonance imaging showed spinal cord edema with mild contrast enhancement at the T9-10 and T12 levels. Although mild venous dilatation was observed only at the cauda equina level, it was not initially recognized as abnormal. Blood and cerebrospinal fluid tests and spinal angiography of the lower thoracic to upper lumbar levels were nonspecific. The patient was unsuccessfully treated with three courses of high-dose intravenous methylprednisolone. Ultimately, following repeat spinal angiography (i.e., including the bilateral internal iliac arteries) that revealed a low-flow sacral dural AVF supplied by the right lateral sacral artery, the patient underwent successful surgical venous AVF occlusion/transection.

Conclusion: In cases of spinal cord edema without perimedullary abnormal flow voids, careful spinal angiography including the sacral spine is necessary even if only minimal venous dilation is initially observed at the cauda equina level.

Keywords: Magnetic resonance imaging; Sacral dural arteriovenous fistula; Spinal dural arteriovenous fistula.

Figure 1:

(a) T1-weighted sequence, (b) T2-weighted sequence, and (c) post-gadolinium T1-weighted sequence – initial magnetic resonance imaging at a local hospital, showing intramedullary edema at T9–10 and T12 levels and a mildly dilated vessel at the cauda equina level (white arrow) without perimedullary vein enlargement. (d) Contrast-enhanced computed tomography image at our hospital, demonstrating a dilated vessel in the right first sacral foramen (black arrow). (e and f) Right internal iliac artery angiograms, showing sacral arteriovenous fistula supplied by the right lateral sacral artery. (g and h) Intraoperative photos showing an arterialized vein (white arrows) along the S1 nerve root visualized early by the indocyanine green without other shunt vessels. (i) Magnetic resonance imaging 5 months after surgery, showing extinguished intramedullary edema.