[Normal pressure hydrocephalus after subarachnoid hemorrhage--with regard to pathogenesis and factors influencing the efficacy of shunt surgery].

Twenty-four adult cases of suspected normal pressure hydrocephalus (NPH) after subarachnoid hemorrhage (SAH) were investigated clinically from the aspect of predicting the efficacy of the shunting procedure. They consisted of 13 men and 11 women, with the mean age of 55-y-o. In addition to checking neurological signs, pre- and postoperative CT scans, RI (or CT) cisternography and bolus infusion test were performed in each of them. Shunt surgery was done, all of which ventriculoperitoneal shunt, in 17 patients. They were divided into three groups, namely, shunt effective group (A), neurologically unchanged group after surgery (B) and worsened group (C). The A group had 8 cases, B had 8 also and C contained only one. Effectiveness of shunt procedure was measured by an improvement in the activity of daily life (ADL). Compared with group B, group A tended to have more cases of delayed onset of NPH (mean days of 112 from SAH attack in group A while 55 days in group B), cases with "trias" (3 against 0) and moderate ventricular dilatation with periventricular lucency (8 against 2). The finding of delayed clearance in cisternogram did not make an accurate judgement in the efficacy of shunt surgery. By using the bolus method of infusion test, the true cause of shunt non-effective ventricular dilatation was suggested to the disturbance of cerebral blood circulation due to elevation of intracranial venous outflow resistance. This suggestion was elicited by the analysis of pressure response curve gained from the bolus injection, in which group A cases mainly reached the baseline pressure within 22 minutes, but on the contrary group B showed more than 22 minutes as a rule.(ABSTRACT TRUNCATED AT 250 WORDS)