Brain tumors complicated by pneumocephalus following cerebrospinal fluid shunting--two case reports.

A 16-year-old male with cerebellar astrocytoma and a 29-year-old male with convexity meningioma, both complicated by hydrocephalus, developed pneumocephalus following tumor removal and shunt emplacement. Both patients underwent ventriculoperitoneal shunt emplacement and total tumor removal, and were discharged from hospital in good condition. After 1 year or 10 months, respectively, pneumocephalus and porencephalic cysts in the temporal lobes developed. Since neuroradiological examination could not locate the bone defects in the skull base, the dura mater covering the anterior cranial fossa was repaired. Fistulae were observed in the cribriform plate in both patients. Postoperatively, one patient showed persistent cerebrospinal fluid rhinorrhea. Intratympanic cerebrospinal fluid retention was demonstrated by tympanic puncture ipsilateral to a porencephalic cyst. The other patient again developed pneumocephalus. Magnetic resonance imaging indicated that the base of the porencephalic cyst was in contact with the tegmen tympani. The dura mater covering the floor of the middle cranial fossa was repaired in both patients, and the symptoms ameliorated. The bone defects in the skull base were apparently deeply involved in the development of the porencephalic cysts, indicating that such cysts provide useful information for locating cranial bone defects.