Flow-regulated versus differential pressure valves for idiopathic normal pressure hydrocephalus: comparison of overdrainage rates and neurological outcome

Abstract

Background: To compare flow-regulated (FR) and differential pressure (DP) valves for treatment of patients with idiopathic normal hydrocephalus (iNPH) focusing on overdrainage and neurological outcome. Methods: This is a retrospective study of patients with iNPH treated with FR and DP valves at a single institution between 2008 and 2018. The neurological status was evaluated retrospectively with the Kiefer scale at baseline, after shunt placement and at the 6-month follow-up. Groups were compared using inverse probability of treatment weighting based on propensity scores. Results: The study cohort consisted of 38 patients treated with FR valves and 49 with DP valves. The mean patient age was 72.0 ± 7.6 years. Based on the Kiefer scale score, neurological improvement at the 6-month follow-up was recorded in 79.6% in the DP group and 89.5% in the FR group (p = 0.252). The overdrainage rates were higher among DP valves (10.2%) than among FR valves (2.6%, adjusted p = 0.002). Valve malfunction occurred in 2.0% in the DP group and 5.3% in the FR group (adjusted p = 0.667). Conclusions: The current study demonstrates a comparable neurological improvement between DP and FR valves, with potentially lower overdrainage rates among FR valves. Long-term studies will be necessary to draw a definite conclusion on FR valves for treatment of iNPH patients.