The patient was a previously healthy 23-year-old white man who presented to the emergency department (ED) complaining of sudden onset of complete lower extremity paralysis. He had felt completely normal that morning when he awoke, but realized he couldn't move his legs when he fell to the floor while trying to get out of bed. He was able to drag himself along the floor and call a friend, who brought him to the ED. He felt well the day prior and had begun to lift weights at the gym. He denied any recent back pain or trauma. He complained of ''sore'' and ''crampy'' legs and mild subjective arm weakness. He denied any fever, chills, or loss of bowel or bladder function. He had felt ''jittery'' recently, but attributed it to school stress. He had no history of heavy metal exposure, recent upper respiratory infection, or known tick bites. He denied any visual complaints, palpitations, dyspnea, cough, diarrhea, rashes, headaches, hearing loss, weight loss, night sweats, or dysuria.The patient had never been hospitalized or had any episodes of weakness. He was not taking any medications and denied medication allergies. His parents were healthy, and he had no children or siblings. There was no family history of any neurologic disease. He admitted to binge drinking alcohol twice a month to significant intoxication and smoked one to two packs of cigarettes a day for ten years. He huffed gasoline once three months ago, but denied inhaling any other substances or any other illicit drug use. He worked as an air conditioning repairman.On examination, the patient's heart rate was 100 beats/min, blood pressure 164/60 mm Hg, re- spiratory rate 20 breaths/min, temperature 36.2ЊC, and SaO 2 98% on room air. He was alert and slightly nervous. He had mild facial acne and an otherwise normal head and neck exam. Cardiac exam showed a regular rate and rhythm with a soft 1/6 systolic murmur at the left upper sternal border. His lungs were clear and the abdominal exam was normal. The rectal exam was normal. His extremities were warm, with normal pulses and no edema. The skin was slightly flushed. On neurologic exam he was alert and oriented, cranial nerves were intact, and his sensory exam was normal throughout. He had 5/5 strength in the upper extremities and 2ϩ/5 strength in the lower extremities. The deep tendon reflexes (DTRs) were depressed in the lower extremities. A Babinski reflex was not present and cerebellar testing was normal.The patient was admitted to the ED's observation unit, and a repeat neurologic exam six hours later demonstrated improved motor strength. Upper extremities were 5/5 strength and lower extremities had improved to 4ϩ/5. He was then noted to have 3ϩ DTRs throughout and one beat of clonus in bilateral Achilles' reflex. Neurology consult was obtained and the patient was admitted to the hospital for further studies. Results of magnetic resonance imaging (MRI) of his brain and spinal cord were normal. His chest x-ray and electrocardiogram were normal. His complete blood count was normal and a chemistry panel fr...