Predictors of outcome in patients with normal pressure hydrocephalus

Despite emerging knowledge over 40 years, the postoperative results after shunt implantations in patients diagnosed for normal pressure hydrocephalus (NPH) did not improve significantly during the last decade. For that reason predictors have to be identified in order to predict preoperatively the course of disease. From 1982 until 2000 we examined in a prospective study 200 patients diagnosed for NPH. From the patients, who were surgically treated by a shunt implantation we could reexaminate 155 (78%) in a meantime interval of seven month after the operation. The NPH was graduated 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 focussed the attention on the possiple predictors: patients age, length of disease, clinical signs - like gait ataxia, dementia and bladder incontinence, aetiology ideopathic/secondary as well as implanted valve type and the value of resistance to cerebrospinal fluid outflow. To measure the outcome we used the NPH-Recovery-Rate, as statistical test the Chisquare according to Pearson. In 80 patients with an early stage NPH (without cerebral atrophy) a short course of disease (< 1 year), a just slight distinct of dementia and an implanted Miethke-Dual-Switch valve were significant predictors for a positive postoperative outcome. The outflow resistance measured in the intrathecal infusion test showed only a minimal relevance for the outcome. Those 75 patients with a late state NPH (with cerebral atrophy) had a better outcome when dementia was not present, the outflow resistance was above 20 mm Hg*min/ml, the CSF tap-test was positive and a Miethke-Dual-Switch valve was implanted.