Indications for valve-pressure adjustments of gravitational assisted valves in patients with idiopathic normal pressure hydrocephalus

Abstract

Background: Modern ventriculoperitoneal shunts (VPS) are programmable, which enables clinicians to adjust valve-pressure according to their patients' individual needs. The aim of this retrospective analysis is to evaluate indications for valve-pressure adjustments in idiopathic normal pressure hydrocephalus (iNPH).

Methods: Patients operated between 2004 and 2011 diagnosed with iNPH were included. Kiefer-Scale was used to classify each patient. Follow-up exams were conducted 3, 6, and 12 months after shunt implantation and yearly thereafter. Initial valve-pressure was 100 or 70 mmH2O. Planned reductions of the valve-pressure to 70 and 50 mmH2O, respectively, were carried out and reactive adjustment of the valve-pressure to avoid over- and under-drainage were indicated.

Results: A total of 52 patients were provided with a Medos-Hakim valve(Codman®) with a Miethke shunt-assistant(Aesculap®) and 111 patients with a Miethke-proGAV(Aesculap®). 180 reductions of the valve-pressure took place (65% reactive, 35% planned). Most patients (89%) needed one or two adjustments of their valve-pressures for optimal results. In 41%, an improvement of the symptoms was observed. Gait disorder was improved most often after valve-pressure adjustments (32%). 18 times an elevation of valve-pressure was necessary because of headaches, vertigo, or the development of subdural hygroma. Optimal valve-pressure for most patients was around 50 mmH2O (36%).

Conclusion: The goal of shunt therapy in iNPH should usually be valve-pressure settings between 30 and 70 mmH2O. Reactive adjustments of the valve-pressure are useful for therapy of over- and underdrainage symptoms. Planned reductions of the valve opening pressure are effective even if postoperative results are already satisfactory.

Keywords: Adjustments; gravitational valve; iNPH; idiopathic normal pressure hydrocephalus; indications; valve-pressure.

Figure 1

Number of valve-pressure adjustments per patient. In most cases (61%), one adjustment was needed. In 29% of cases, valves were adjusted twice, in 7% three times, in 2% four times, and in 0.6% (one patient) to optimize clinical outcome

Figure 2

Clinical improvement and worsening of symptoms after valve-pressure adjustments. After 33% adjustments an improvement of gait, after 20% an improvement of cognitive abilities, after 19% a reduction of vertigo, after 15% fewer headaches, and after 13% an improvement of bladder control were seen. Gait disorder worsened most often after valve-pressure reduction (36%); cognitive decline (10%), vertigo and headaches (15%), and urinary incontinence (24%) showed an aggravation less often

Figure 3

Optimized valve-pressure. A total of 83% patients were treated best with valve-pressures between 30 and 70 mmH₂O