The Importance of the Intrathecal Infusion Test in the Diagnostic of Normal-pressure Hydrocephalus

Objective: The intrathecal infusion test is a reliable method for diagnosing normal-pressure hydrocephalus (NPH).

Methods: Between May 1982 and January 1997, we investigated 200 patients suspected of having NPH by carrying out an intrathecal infusion test with a constant-flow technique. The resistance to cerebrospinal fluid outflow in the intrathecal infusion test was the main criterion for grouping patients into those with NPH or those with cerebral atrophy. A further differentiation into early stage and advanced stage was made by measuring the compliance, this being the secondary criterion.

Results: In 107 patients (54%), the diagnosis of 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 at an early stage and an advanced stage allows prognostic evaluations about the course of disease to be made. Patients with NPH at an early stage reported an improvement of their symptoms in the follow-up after a shunt operation in 65% of cases, while 50% of those with advanced-stage NPH reported improvement.

Conclusion: The computer- aided infusion test allows a reliable differentiation between patients with NPH and those with cerebral atrophy.