[A case of tension pneumocephalus due to scalp-ventricle fistula following trepanation after a 9-year interval].

We report a case of tension pneumocephalus due to scalp-ventricle fistula following trepanation surgery after a 9-year interval. A 68-year-old man had a past history of subarachnoid hemorrhage (unknown etiology) in 1987. At that time, he underwent an operation for ventriculoperitoneal (V.P) shunt and subduroperitoneal (S.P) shunt following ventricular drainage for hydrocephalus. He was admitted to our hospital with generalized convulsions on Feb. 26, 1996. On admission, he presented with disoriented consciousness and mild left hemiparesis. The skull films and CT showed abundant air collection in the bifrontal lobe mainly in the bilateral anterior horns of the lateral ventricle. We initially suspected air entry from frontal skull base fracture. However, a dimple was found on the right frontal scalp and connection between the dimple and the intracranial space was detected by fistulography. Scalp-ventricle fistula following trepanation was proved to be the air entry and it brought about tension pneumocephalus. On Mar. 6, closure of the fistula with a rotation skin flap was achieved. The collected air was completely absorbed, but a low-density area in the right frontal lobe remained on CT examination. We surmised that irreversible brain damage had been caused by longtime air exposure injury.