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[Tension pneumocephalus in association with ventriculoperitoneal shunt and congenital bony defect in the mastoid tegmen].

The authors report a case of tension pneumocephalus in association with a congenital bony defect at the mastoid tegmen, and a ventriculoperitoneal (V-P) shunt for obstructive hydrocephalus, due to the presence of a posterior fossa meningioma. After multiple diagnosis and surgical procedures, congenital bony defect at the right mastoid tegmen demonstrated by a middle ear cavity computerized tomography (CT) scan, was identified as the source of entry of the air. The air must have penetrated the lateral ventricle through a porencephalic cyst in the right temporal lobe. Reconstruction of the bony defect in the mastoid tegmen successfully prevented further recurrence of tension pneumocephalus. We discussed the possible pathogenic mechanisms involved in this kind of tension pneumocephalus, and suggested that a middle ear cavity CT scan should be performed for tension pneumocephalus that has developed after V-P shunt.