Doctors at Zuckerberg San Francisco General Hospital could not figure out what was wrong with the 29-year-old man sitting before them. An otherwise healthy construction worker from Nicaragua, the patient was suffering from a splitting headache, double vision and ringing in his ears. Part of his face was also numb. The cause could have been anything—from an infection to a stroke, a tumor or some kind of autoimmune disease. The Emergency Department (ED) staff took a magnetic resonance imaging scan of the man’s brain, performed a spinal tap and completed a series of other tests that did not...…Doctors at Zuckerberg San Francisco General Hospital could not figure out what was wrong with the 29-year-old man sitting before them. An otherwise healthy construction worker from Nicaragua, the patient was suffering from a splitting headache, double vision and ringing in his ears. Part of his face was also numb. The cause could have been anything—from an infection to a stroke, a tumor or some kind of autoimmune disease. The Emergency Department (ED) staff took a magnetic resonance imaging scan of the man’s brain, performed a spinal tap and completed a series of other tests that did not...WW…