A double-blind randomized trial on the clinical effect of different shunt valve settings in idiopathic normal pressure hydrocephalus

OBJECTIVE The study aim was to examine the effect of gradually reducing the opening pressure on symptoms and signs in the shunt treatment of idiopathic normal pressure hydrocephalus (iNPH). METHODS In this prospective double-blinded, randomized, controlled, double -center study on patients with iNPH, a ventriculoperitoneal shunt with an adjustable Codman Medos Valve was implanted in 68 patients randomized into 2 groups. In 1 group (the 20-4 group) the valve setting was initially set to 20 cm H2O and gradually reduced to 4 cm H2O over the course of the 6 -month study period. In the other group (the 12 group), the valve was kept at a medium level of 12 cm H2O during the whole study period. All patients were clinically evaluated using 4 tests preoperatively as well as postoperatively at 1, 2, 3, 4, and 6 months. The test scores between the 2 groups (20-4 and 12) were compared for each clinical evaluation. RESULTS Fifty-five patients (81%) were able to complete the study. There were no significant differences between the 2 groups (20-4 and 12) preoperatively or at any time postoperatively. Both groups exhibited significant clinical improvement after shunt insertion at all valve settings compared with the preoperative score, with the greatest improvement observed at the first postoperative evaluation. The clinical improvement was-significant within the first 3 months, and thereafter no significant improvement was seen in either group. CONCLUSIONS Gradual reduction of the valve setting from 20 to 4 cm H2O did not improve outcome compared with a fixed valve setting of 12 cm H2O. Improvement after shunt surgery in iNPH patients was evident within 3 months, irrespective of valve setting.