gms | German Medical Science

Objective: Overdrainage and frequent reprogramming are common issues with programmable differential pressure (DP) valves after ventriculoperitoneal shunt surgery for idiopathic normal pressure hydrocephalus (iNPH). Non-programmable, flow-regulated (FR) valves may address these limitations, however, there are concerns about their safety and efficacy. Thus, we retrospectively compared FR and DP valves in terms of complication rates and neurological outcome.

Methods: The authors reviewed consecutive patients treated with a non-programmable FR valve (drainage rate: 8–17 ml/h) or a programmable DP valve at a single institution between 2008 and 2018. All valve-related complications that required surgical revision were recorded. The Kiefer Scale (KS) was used to assess the neurological status before surgery and at 6-month follow-up. The KS allows a retrospective scoring of iNPH and consists of the fives subdomains including gait, cognitive impairment, incontinence, headache and dizziness. Neurological outcome was evaluated by the iNPH-Recovery Rate (iNPH-RR), which is calculated based on the pre- and postoperative KS score. Comparisons between groups were performed using the unpaired Student’s t-test, the Mann-Whitney U test and the Chi-Square test, when appropriate.

Results: A total of 66 patients (FR: 36, DP: 30) were enrolled. The two groups were comparable in terms of patient age (71.4±8.3 years vs. 71.0±6.9 years, p=0.8), duration of symptoms before surgery (22.1±12.5 months vs. 22.4 vs. 23.5 months, p=1.0) and preoperative KS score (7.4±1.8 vs. 6.8±1.9, p=0.3). At 6-month follow-up, the mean KS score was 3.0±2.4 in the FR group and 4.2±3.2 in the DP group (p=0.18). The iNPH-RR was significantly higher in the FR group (6.0±3.2) than in the DP group (3.8±4.7, p=0.04), indicating a better neurological outcome after implantation of flow-regulated valves. The complication rate was 8.3% (3/36) in the FR group (subdural hygroma: 2, shunt dysfunction: 1) and 16.7% (5/30) in the DP group (subdural hygroma: 5) (p=0.5).

Conclusion: In our study, FR valves yielded a better neurological outcome than DP valves, with similar complication rates and potentially lower overdrainage rates. Long-term follow-up will be necessary to draw a definite conclusion on the use of non-programmable FR valves for treatment of iNPH.