Patients benefit from low-pressure settings enabled by gravitational valves in normal pressure hydrocephalus

The ability of siphon regulatory devices to improve overdrainage control despite low-pressure settings of the valve for the horizontal body position has been described previously. We aim to provide a systematic investigation on the ability of gravitational units as siphon regulatory devices to improve clinical outcome in shunt therapy.

We analyzed retrospectively postoperative complications, type and frequency of valve adjustments and the clinical outcome using Black's outcome scale at different time points of all iNPH patients operated in our center between January 2007 and December 2010. They had received either a proGAV® valve with an integrated gravitational unit, or a programmable Codman Hakim® valve without an integrated siphon regulatory device.

The postoperative course of 55 proGAV® and 45 programmable Codman Hakim® patients was analyzed. The latest documented valve setting of the proGAV® group and Codman Hakim® group was median 50mm H2O and 120 mm H2O, respectively. Overdrainage occurred among both groups in 20% of the patients, while surgical intervention for overdrainage-related complications was seen to be necessary only in 7% of the cases in the Codman Hakim® group. Clinical outcome differed in an increasing manner over the observation period (median 4 points after 3, 12 months and at final presentation in the proGAV®; median 4 points after 3 and 12 months and 3 points at final presentation in Codman Hakim® group (p=0.001)).

Adjustable and gravity-assisted valves like the proGAV® improve overdrainage control and enable thus low-pressure settings for the horizontal body position. We observed an improved and more sustainable functional outcome for iNPH patients with an adjustable and gravity-assisted valve compared to iNPH patients without an integrated siphon regulatory device.