# Reduced risk of shunt revision with adjustable valves: a population-based cohort study over three decades

## TL;DR

Adjustable shunt valves reduce the need for revision surgeries in patients with idiopathic normal pressure hydrocephalus compared to fixed-pressure valves.

## Contribution

This study provides population-based evidence that adjustable valves lower shunt revision rates over a 30-year period.

## Key findings

- Adjustable valves had a 14% revision rate compared to 30% with fixed-pressure valves.
- Peritoneal catheter malposition was the most common cause of revision in the adjustable valve group.
- Shunt underdrainage was the most common cause of revision in the fixed-pressure valve group.

## Abstract

Idiopathic normal pressure hydrocephalus (iNPH) is a neurological disease characterized by ventriculomegaly and Hakim’s triad. At present, symptoms can be alleviated only by cerebrospinal fluid (CSF) shunt surgery. Yet, various complications after shunting may occur, occasionally requiring repeated shunt revisions. In this retrospective, population-based study, our objective was to compare revision rates and causes for revision surgeries between adjustable shunt valve and fixed-pressure valves in iNPH patients.

Altogether 1220 patients were evaluated for possible iNPH at Kuopio University Hospital between 1991 and 2023. Probable iNPH was diagnosed in 809 patients who received their first ventriculoperitoneal shunt (VPS). Of the patient cohort, 566 were shunted using an adjustable valve (2008–2023) and 243 received a fixed pressure valve (1991–2012). Hospital records and nationwide registries were used to construct a timeline for each patient from the shunt insertion and until death (n = 430) or the end of 2023.

Overall revision rate was lower in iNPH patients receiving an adjustable valve (14% vs. 30%, p < .001, 95% CI 0.27—0.56). The incidence of multiple revisions was also lower in the adjustable valve group (27% vs. 32% p = 0.002, 95% CI 0.21—0.71). The most common cause for revision was peritoneal catheter malposition in the adjustable valve group (44%) and shunt underdrainage in the fixed-pressure valve group (25%).

Adjustable shunt valves have decreased the need for shunt revision surgeries due to under- and overdrainage.