[Intracranial pneumocephalus under pressure. A possible cause of postoperative deterioration in neurosurgery. 10...

10 patients in whom an early post operative alteration of the level of consciousness or of the neurological status could be related to a tension pneumocephalus are reviewed. Four underwent a surgical procedure in the sitting position. Among these, 2 had been previously shunted for hydrocephalus. A 5th patient underwent a IIId ventriculocisternostomy for tumorous occlusion of the aqueduct. The other five patients were involved with supra-tentorial conditions (hemispheric glioma: 1 case, meningioma: 1 case, chronic subdural hematoma: 3 cases). The post-operative deterioration clinically suggested a post operative hematoma. CT showed a very low density effusion either located in the operative area or in the subdural space or both, with significant mass effect. 9 patients steadily improved after conservative therapy. In 1 case, reoperation was required. Pathogenesis of symptomatic pneumocephalus remains controversial. The role of the sitting position and of CSF drainage seem likely. Spontaneous or nitrous oxide induced expansion of post-operative residual intra cranial air plays a debatable role. It is postulated that tension pneumocephalus may result from a discrepancy between spontaneous reexpansion of the cerebral mass and a residual air collection. Such complications are regarded as serious enough to justify several preventive measures.