Object: This study was undertaken to investigate whether a gradual reduction of the valve setting (opening pressure) decreases the complication rate in patients with idiopathic normal-pressure hydrocephalus (iNPH) treated with a ventriculoperitoneal (VP) shunt.
Methods: In this prospective double-blinded, randomized, controlled, dual-center study, a VP shunt with an adjustable valve was implanted in 68 patients with iNPH, randomized into two groups. In one 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 pressure setting of 12 cm H₂O during the whole study period. The time to and type of complications (hematoma, infection, and mechanical problems) as well as overdrainage symptoms were recorded. Symptoms, signs, and outcome were assessed by means of the iNPH scale and the NPH grading scale.
Results: Six patients in the 20-4 group (22%) and 7 patients in the 12 group (23%) experienced a shunt complication; 9 had subdural hematomas, 3 mechanical obstructions, and 1 infection (no significant difference between groups). The frequency of overdrainage symptoms was significantly higher for a valve setting ≤ 12 cm H₂O compared with a setting > 12 cm H₂O. The 20-4 group had a higher improvement rate (88%) than the 12 group (62%) (p = 0.032). There was no significant relationship between complications and body mass index, the use of an antisiphon device, or the use of anticoagulants.
Conclusions: Gradual lowering of the valve setting to a mean of 7 cm H₂O led to the same rate of shunt complications and overdrainage symptoms as a fixed valve setting at a mean of 13 cm H₂O but was associated with a significantly better outcome.
Keywords: ASD = antisiphon device; ICP = intracranial pressure; NPH = normalpressure hydrocephalus; PL = performance level; SDH = subdural hematoma; VP = ventriculoperitoneal; iNPH = idiopathic NPH; normal-pressure hydrocephalus; opening pressure; postoperative complications; randomized controlled trial; shunt surgery; subdural hematoma.