National and regional incidence of surgery for adult hydrocephalus in Sweden.

In Sweden, the annual incidence of surgery for hydrocephalus was 3.4 per 100,000 adults between the years 1996 and 1998. The most common indication for surgery was normal pressure hydrocephalus (NPH; 47%), followed by high-pressure hydrocephalus (27%). Seventy-three percent of the patients had communicating hydrocephalus, of which 63% had NPH. Twenty percent of the patients had non-communicating hydrocephalus, of which half resulted from aqueduct stenosis. The annual incidence of operations varied between regional clinics from 2.3 to 6.3 per 100,000 inhabitants.