Predictors of outcome in patients with normal-pressure hydrocephalus.

From 1982 until 2000 we examined 200 patients diagnosed with normal-pressure hydrocephalus (NPH) in a prospective study. From the patients who were surgically treated by a shunt implantation we could re-examine 155 (78%) at a mean time interval of 7 months after the operation. NPH differed in severity according to the results of the intrathecal infusion test in an early state NPH (without brain atrophy) and late state NPH (with brain atrophy). In our study, we focused on the possible predictors: patient age; length of disease; clinical signs including gait ataxia, dementia, and bladder incontinence; idiopathic vs. secondary origin; implanted valve type and the resistance of the valve to cerebrospinal fluid outflow. In 80 patients without cerebral atrophy and a short course of disease (< 1 year), a slight amount of dementia and an implanted Miethke Dualswitch-Valve were significant predictors for a positive postoperative outcome. The outflow resistance measured in the intrathecal infusion test showed only minimal relevance for outcome. Seventy-five patients with cerebral atrophy had a better outcome when dementia was not present, outflow resistance was above 20 mmHg/mL/min, the CSF tap-test was positive, and a Miethke Dualswitch-Valve was implanted.