A 59-year-old man was admitted to this hospital with fever and the subacute onset of progressive neurologic symptoms that included multiple cranial-nerve palsies. Magnetic resonance imaging of the brain and spine showed leptomeningeal enhancement. Analysis of the cerebrospinal fluid disclosed a lymphocytic pleocytosis and elevated protein and glucose levels. Respiratory failure developed, requiring intubation and mechanical ventilation. The result of a diagnostic test was received.