A Rare Case of Intracerebral Pneumocephalus Caused by Preexisting Multiple Bone Defects and Encephalocele after Resection of Meningioma.

Pneumocephalus is generally secondary to direct damage to the skull base. Spontaneous intracerebral pneumatocele without head injury was extremely rare, but previously reported as a serious complication of shunt procedures. We describe a 40-year-old man with intracerebral pneumocephalus who previously underwent craniotomy for large frontal convexity meningioma and lumbo-peritoneal shunting. He presented with gait disturbance 14 months after tumor resection. Computed tomography and magnetic resonance imaging showed intracerebral pneumocephalus in the right temporal lobe, which continued into the mastoid air cells through a bone defect of the right petrous bone. We performed urgent right temporal craniotomy to reduce the mass effect and to repair the fistula. Intraoperatively, bone defects were identified at the roof petrous bone, into which the encephalocele had penetrated. The herniated cerebral parenchyma was removed, and the pneumocephalus opened. The dura was closed with sutures and covered with fascia. To elucidate the underlying mechanism for the development of intracranial pneumocephalus, the previous images obtained before or immediately after resection of meningioma were reviewed. We founded that multiple preexisting bone defects and encephaloceles, one of which was considered to be the cause of the intracerebral pneumocephalus. This case demonstrates that intracerebral pneumocephalus can be caused by preexisting bone defect and encephalocele, and this finding may be useful for prediction of pneumocephalus after shunt procedures.