[Normal pressure hydrocephalus--evaluation of investigation procedures]

58 patients were investigated with a lumbar infusion test for normal pressure hydrocephalus in the department of neurology of the National Hospital between January 1991 and December 1996. We present a retrospective evaluation of the investigation protocol for these patients with suspected normal pressure hydrocephalus. The aim of the study was to find out whether specific prognostic factors could be identified by routine investigations. 20 patients had been referred to the department of neurosurgery and were subsequently shunted. A critical review of the criteria leading to surgical treatment (clinical symptoms, cerebral CT scan, infusion test, cisternography) is presented. There was no single variable which alone could discriminate normal pressure hydrocephalus from other types of hydrocephalus, or predict the outcome of shunting. A more systematic referral and clinical assessment of the patients together with a more precise evaluation of the findings and improved follow-up procedures are necessary for optimal selection of patients for surgery. The study also shows the importance of diagnosing these patients early, as delay in treatment appeared to worsen prognosis after shunting.