gms | German Medical Science

Objective: After ventriculoperitoneal shunt surgery for idiopathic normal pressure hydrocephalus (iNPH) with adjustable gravitational valves, a certain proportion of patients develop secondary clinical worsening after initial improvement of clinical symptoms. The aim of this study was to analyze this group of patients with secondary deterioration and to evaluate the performed shunt management.

Methods: We retrospectively reviewed our prospective NPH registry. Patients who showed equal or worse Kiefer scores (KS) in the first year of follow up compared to the preop score where defined as "primarily deteriorated". "Secondary deterioration" was defined as a decrease by the min of 2 points in the KS in the first year of follow-up and an increase of 2 points in the KS between the second and the fifth year after shunt surgery. Patients with secondary deterioration resulting from a treatable shunt issue (adaption of the pressure setting, shuntography, surgical revision) were defined as "shunt insufficiency". Patients with secondary deterioration and unsuccessful shunt management were assigned as "secondary non- responder". Then, we searched for risk factors.

Results: Out of 353 patients, 53 (15 %) patients showed secondary deterioration on an average of 2,7 years after shunt surgery. Fourteen (26%) patients with secondary deterioration improved after shunt / valve management, 58% remained without clinical benefit after taking action of the VPS. We had a drop-out rate of 15% due to incomplete datasets. Our shunt management reduced the rate of secondary deterioration from 15% to 8%. On the basis of our findings, we developed an algorithm to decrease the rate of "secondary non-responder". Risk factors for becoming "secondary non-responder" patient’s age at the time of shunting, newly diagnosed neurodegenerative diseases and overdrainage requiring adjusting the valve to higher-pressure levels.

Conclusion: Fifteen percent of patients with NPH are at risk for secondary clinical worsening about 3 years after shunt surgery. About one fourth of these patients benefit for additional years from pressure level management and / or shunt valve revision. Our findings underline the need for long-term follow-ups and intensive shunt management to achieve a favorable long-term outcome for patients with NPH and VPS.