A Rare Case of Thoracic Spinal Dural Arteriovenous Fistula Emerging Gradually after Lumbar Decompression, Requiring Direct Transection

A 67-year-old man presented with progressive bilateral numbness in the lower extremities and intermittent claudication.Seven years prior, he had undergone L3/4 and L4/5 lumbar decompression for spinal canal stenosis.Although his initial postoperative recovery was favorable, sensory disturbances gradually re-emerged, predominantly affecting the left lower extremity, persisted even at rest, and proved refractory to conservative treatment.Subsequently, the patient developed urinary frequency and symptoms of incomplete bladder emptying.Lumbar magnetic resonance imaging (MRI) conducted 5 years after surgery demonstrated sustained decompression without restenosis; however, intramedullary signal changes and newly developed perimedullary flow voids were observed on sagittal T2weighted images.These abnormalities progressed on MRI performed 7 years postoperatively, with more pronounced serpiginous perimedullary flow voids along the dorsal spinal cord (Figure 1A andB).Additional thoracic MRI revealed longitudinal spinal cord edema with dilated perimedullary vessels and flow voids (Figure 2A-C).Spinal angiography revealed a spinal dural arteriovenous fistula supplied by the right sixth intercostal artery (Figure 2D).The final preoperative neurological examination revealed cauda equina-type intermittent claudication, with a Japanese Orthopedic Association score of 15/29 points.Deep tendon reflexes were normal in all extremities before the initial lumbar surgery.However, at presentation for the current surgery, deep tendon hyperreflexia of the lower extremities and a positive Babinski sign were observed.Microsurgical direct transection was performed, resulting in disconnection of the abnormal vessel (Figure 3A andB).Postoperative neurological recovery was favorable, with gradual