Infarct of the conus medullaris simulating a spinal cord tumor: case report. A 71-year-old woman had the sudden onset of a neurogenic bladder and a stepwise increase in paraparesis that left her unable to stand or walk. Magnetic resonance imaging showed what appeared to be a tumor in the conus medullaris. After laminectomy, the lesion was localized by ultrasound examination, and a biopsy was performed. The deficits remained unchanged postoperatively. Microscopic examination of the biopsy specimen showed necrosis and pathologic changes consistent with infarction of the conus medullaris. An anomalous arterial supply of the conus medullaris is the most likely cause of this unusual problem. The patient gradually regained her ability to walk, but the neurogenic bladder persists. 