Clinical reasoning: a 20-year-old woman with rapidly progressive weakness.

A 20-year-old healthy woman developed abdominal pain accompanied by mild frontal headaches, labile mood, vomiting, and dark urine. She underwent an extensive workup including endoscopy, abdominal CT scan, and eventually exploratory laparotomy. No abdominal cause of her symptoms was detected and she was discharged. Approximately 1 week after surgery, she developed low back pain and numbness in the buttocks and upper thighs. Within several days, her sensation was reduced in her hands and she developed generalized weakness. Her only medication was an oral contraceptive, which was started 1 month before onset of abdominal symptoms. She presented to our institution 3 weeks after symptom onset and reported diffuse weakness, most prominent in the proximal arms. She still had mild pain and numbness in the abdominal area, low back, and buttocks, but the numbness in the arms and legs had subsided. Neurologic examination revealed profound symmetric weakness in the proximal arms and moderate weakness in the proximal legs. Sensory examination demonstrated a band-like area of decreased sensation to pinprick in the lower abdomen and low back. Deep tendon reflexes were 2+ at the biceps and triceps and 3+ at the knees. Hoffmann sign was present on both sides. There were 1 to 2 beats of unsustained ankle clonus bilaterally. Plantar responses were flexor. Cranial nerve examination was normal.