The importance of the intrathecal infusion test in the diagnostics of normal pressure hydrocephalus.

OBJECTIVE: The intrathecal infusion test is a reliable method in diagnosing normal pressure hydrocephalus. METHODS: Between May 1982 and January 1997 we investigated 200 patients suspected for a normal pressure hydrocephalus (NPH) by carrying out an intrathecal infusion test in a constant flow technique. The resistance to cerebrospinal fluid outflow (Rout) in the intrathecal infusion test was the main criterion for grouping patients into these with normal pressure hydrocephalus or those with cerebral atrophy. A further differentiation into early stage and late stage was made by measuring the compliance (Cp)--this being the secondary criterion. RESULTS: In 107 patients (54%) the diagnosis of a NPH could be confirmed. Of these, 102 patients (95%) underwent a shunt operation. Graduation of NPH and cerebral atrophy following the results of the infusion test in an early stage and an advanced stage allows the conclusion of prognostic evaluations about the course of disease to be made. Patients with a NPH in an early stage are reporting in the follow up about an improvement of their symptoms after a shunt operation in 65 percent of cases and those with an advanced stage NPH in 50 percent. CONCLUSION: The computer aided infusion test allows a reliable differentiation between patients with NPH and those with cerebral atrophy.