Chronic meningitis presenting with acute obstructive hydrocephalus.

A previously healthy 24-year-old woman presented to the Emergency Department unresponsive with a Glasgow Coma Scale score of 4 and evidence of brainstem herniation. She was intubated and hyperventilated. Computed axial tomography scan of the brain demonstrated four-chamber hydrocephalus. Continued hyperventilation and mannitol diuresis were sufficient to arrest the impending herniation while emergent ventriculostomy was arranged. The patient recovered without sequelae and ultimately received a diagnosis of chronic idiopathic meningitis. This case highlights a rarely diagnosed disorder that presented with an acutely life threatening condition.