The Impact of Programmable Valves on the Risk and Severity of Subdural Collections in Patients With Normal Pressure...

Normal pressure hydrocephalus (NPH) is characterized by the classic triad of cognitive decline, gait instability, and urinary incontinence in the setting of ventriculomegaly with normal intracranial pressure. Cerebrospinal fluid diversion is the current standard treatment, yet it carries a risk of overdrainage, resulting in subdural hematoma or hygroma. Different valves have been developed to mitigate this risk, yet consensus remains unclear regarding optimal valve for NPH.

We performed a retrospective cohort study on all patients with NPH who underwent cerebrospinal fluid shunting or revision between January 2014 and September 2025 at our institution. Demographic, clinical, and radiological data were collected from the electronic health record. Kaplan-Meier survival analysis, univariate logistic regression, and multivariate modeling were used to identify predictors of subdural collections and the need for surgical treatment.

Since our change in practice from the Integra NPH Low Flow Valve (Low Flow OSV) to other valves in 2022, we observed a rise in symptomatic subdural collections. Programmable valves were associated with a markedly increased 1-year risk of both subdural collection formation and need for surgical intervention compared with the Low Flow OSV. Overall, Certas and Strata valves demonstrated higher rates of subdural collections requiring surgery than the Low Flow OSV (14.6% vs 2.1%, P < .001; 10.5% vs 2.1%, P = .005, respectively). On multivariate analysis, both the Strata and Certas valves were independently associated with increased odds of developing any subdural collection and necessitating surgery. Vascular disease and dual antiplatelet therapy also increased risk.

In this large single-center cohort study, programmable valves, specifically the Certas and Strata, were associated with an increased rate and severity of subdural collections compared with the Low Flow OSV. The use of low-flow designs may mitigate complications for the NPH population, and the use of lower programmable valve settings should be carefully considered.