Otogenic pneumocephalus associated with a ventriculoperitoneal shunt.

Otogenic pneumocephalus is a condition of intracranial air originating from the middle ear or mastoid air cells. This communication between the intracranial cavity and the pneumatic cavities is usually associated with trauma after cranial fractures or iatrogenic trauma. We present a rare case of otogenic pneumocephalus arising in the left posterior fossa from wellpneumatized mastoid air cells. The patient complained of roaring tinnitus that developed 29 months after ventriculoperitoneal shunt insertion due to brain tumor surgery. High resolution computed tomography scan of the temporal bones revealed a large pneumocephalus below the left tentorium, and a bony dehiscent route was clearly identified in a sagittal view. A left mastoidectomy with preservation of the posterior wall of the external auditory canal was performed, and the expected bony dehiscent site was identified in the posterior fossa dura plate, just posterior to the posterior semicircular canal, below the Donaldson's line. This communication was sealed with a temporalis muscle plug from the deep temporalis muscle fascia and bone dust. Pneumocephalus may be caused by negative intracranial pressure in a patient with very well-pneumatized mastoid bone, and it can be a possible cause of 'wind-like' sound in the ear.