Recurrent Meningitis in an 11-year-old Girl with a Petrous Apex Cystic Lesion.

Cases of recurrent meningitis in elderly patients with a spontaneous cerebrospinal fistula have been reported, and in some of these patients, cystic lesions were thought to be the underlying cause. We report a case of recurrent meningitis in an 11-year-old Japanese girl with an arachnoid cyst in the petrous apex. Pulsation of the cystic lesion was thought to cause bone erosion, leading to the formation of a fistula. Magnetic resonance imaging was useful in evaluating the arachnoid cyst and fistula. During 2 years of follow-up, the osteolytic lesion enlarged and the rate of bone erosion was higher than expected.