Pneumocephalus associated with benign brain tumor: report of two cases.

Two cases of spontaneous pneumocephalus, which developed after ventriculoperitoneal shunt procedures for severe hydrocephalus caused by benign brain tumors, are reported. In both cases there was no previous history of cerebrospinal fluid leakage. Operation revealed that both patients had many small defects of the dura mater and the bone in the middle cranial fossa, which were plugged by necrotic brain tissue. These defects were remote from the sites of the original tumors but may have been produced by long-standing raised intracranial pressure, and they presumably allowed air to enter after intracranial pressure was reduced by shunting. Repair of the defects prevented further intracranial air retention.