A 77-year-old man presents with acute inability to walk. There is nohistory of trauma or back pain, and he has no bladder, bowel, or radicular symptoms. Medical history is significant only for benign prostatic hypertrophy. He takes no medication, has never smoked, drinks negligible alcohol, and prior to this episode was fully independent. On physical examination, the left lower extremity has reduced motor strength at 2/5 throughout, with depressed reflexes (2/4 knee and ankle jerks) and subjective, nondermatomal light-touch sensory loss. Plantar reflexes are down-going bilaterally. Right lower extremity strength and anal tone are normal, and there is no vertebral tenderness. Cardiac, pulmonary, and abdominal examination results are normal. There are multiple, tender, blue-black cutaneous swellings of up to 1-cm diameter across the upper torso/shoulders (Figure 1), which he says have been present for many years. He quickly deteriorates, developing profound bilateral leg weakness.