Mollaret's recurrent aseptic meningitis and cerebral epidermoid cyst.

A patient who initially presented with clinical and laboratory signs of bacterial meningitis developed four more similar episodes within a 6-month period. Immune system studies were unremarkable. A tentative diagnosis of Mollaret's meningitis was established after the third episode. Cranial computed tomography performed during the acute phase of the initial episode was normal, but, after the fourth scan, when the patient was asymptomatic, magnetic resonance imaging revealed a cyst in the anterior aspect of the medulla. Partial excision allowed for pathologic analysis, which established the diagnosis of epidermoid cyst. The differential diagnosis of recurrent aseptic meningitis should include Mollaret's meningitis and dermoid-epidermoid cysts. Neuroimaging studies, preferably magnetic resonance imaging, should be performed at a time when patients are asymptomatic.