Spinal dural arteriovenous fistulas (SDAVFs) are the most common type of spinal vascular malformation. The arteriovenous shunts, located entirely outside the spinal cord, cause a clinical picture of chronic progressive myelopathy believed to arise from the effects of increased venous pressure and impaired venous drainage on the spinal cord. Despite their well-described clinical and angiographic features, no reports have documented the spinal cord pathology in a case of angiographically or pathologically proven SDAVF. We report such a patient in whom a spinal cord biopsy supported increased venous pressure as a mechanism of neurologic dysfunction.