Although setting a low initial opening pressure in a programmable valve with a gravitational unit seems to be the gold standard treatment for idiopathic normal pressure hydrocephalus (iNPH) patients, there are no studies in the literature describing the optimal initial low-pressure setting. Here, we sought to describe the optimal initial opening pressure setting for iNPH in terms of both efficacy and safety.

Patients with probable iNPH underwent shunt surgery with a programmable valve with a gravitational unit, using either an opening pressure of 3 or 6.5 cmH2O, and were prospectively followed for 1 year. Clinical improvement and complications were recorded.

Nineteen patients with an opening pressure of 3 cmH2O and 37 patients with an opening pressure of 6.5 cmH2O were analyzed. There was no significant difference between the groups. A significant improvement in the iNPH Japanese scale score was observed 1 year following shunt placement in both the 3.0 cmH2O (p = 0.001) and 6.5 cmH2O groups (p < 0.001), but there was no statistical difference between groups (p = 0.708). Two patients (10.5%) had subdural effusions that required surgery in the 3 cmH2O group and none in the 6.5 cmH2O group (p = 0.043).

Patients with iNPH treated with a programmable valve with an initial opening pressure of 6.5 cmH2O showed the same clinical improvement as those treated with an initial opening pressure of 3 cmH2O but with fewer overdrainage complications.

Received: 29 July 2025

Accepted: 20 January 2026

Accepted Manuscript online:
22 January 2026

Article published online:
11 June 2026

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