Spinal dural arteriovenous fistula presenting as progressive thoracic myelopathy

A 51-year-old man had a 4-month history of back pain and progressive leg weakness. The back pain was on the left side, radiating down his left buttock and leg to the dorsum of the foot. He had gradually developed bilateral leg weakness with a right foot drop such that he required a four-wheeled walker. There was accompanying left anterior thigh numbness and saddle anaesthesia, together with urinary urgency and one episode of faecal incontinence. He had been previously well, though 13 years before had sustained a non-specific back injury in a motor vehicle collision that did not require surgical intervention.\n\nOn examination, there were lower limb hyperreflexia, patchy sensory loss in all modalities in both legs, a positive Beevor’s sign (upward movement of the umbilicus with attempted neck flexion due to weakness of the lower rectus abdominis)1 and absent rectal tone. Muscle strength was normal in the upper limbs, but 2/5 bilaterally in hip flexion, 4/5 bilaterally in knee flexion and extension, and 4–/5 …