Development of a quick reference table for setting programmable pressure valves in patients with idiopathic normal pressure hydrocephalus

Abstract

Quick and reliable setting of programmable pressure valves (PPVs) is important in the treatment of idiopathic normal pressure hydrocephalus (iNPH), especially for reducing overdrainage complications and related medical costs. A new quick reference table (QRT) was developed for improved PPV control and outcome. Shunt control can be based on the pressure environment in the sitting condition, given as hydrostatic pressure (HP) = intracranial pressure + PPV setting + intraabdominal pressure (IAP). Using this relationship, and estimating HP and IAP from the patient's height and body mass index, respectively, a QRT was designed, consisting of a matrix of the patient's height and weight. The QRT was used to make initial PPV settings in 25 patients with iNPH and the clinical outcomes were evaluated. Postoperative readjustments of the PPV were not necessary in 15 of the 25 patients. At 1 month after operation, the PPV setting was decreased once in 5 patients and increased once in 2 patients. Four of these 7 patients improved after a single readjustment. Three patients required further readjustments. At 3 months after operation, another 3 patients required a single readjustment and all improved after this readjustment. The readjustment rate was 40% and readjustment number was 0.68 times/patient. The mean PPV setting at 1 year after operation was 15.5 ± 3.9 cmH2O. Use of the QRT in non-bedridden iNPH patients results in a low incidence of PPV readjustment.