First experiences with Miethke M.blue® valve in iNPH patients

•Positive clinical effect was found in 21 shunted iNPH patients at three months follow-up.•The highest response was found in gait. Incontinence was mitigated.•Although MoCA results remained stable, specific tests showed that learning and executive abilities slightly improved.•We recommend increasing the initial valve setting by 2–4 cm H2O above manufacturer’s recommendation, especially in lean patients. The literature on hydrocephalus treatment shows support for adjustable valves and devices which prevent the so-called “siphon effect”. In our study, 21 probable iNPH patients were indicated to shunt surgery with the Miethke M.blue® adjustable gravitational valve. Outcomes at three months were measured using the following tests: Dutch Gait Scale, International Consortium on Incontinence Questionnaire (ICIQ-UI SF), SF12V2-Health Survey, Kiefer Scale, 3T MRI, and a neuropsychological testing battery. Preoperative parameters were studied for any signs of overdrainage risk. Valves were set according to the manufacturer's recommendations. Significant improvement at three months was seen in the Dutch Gait Scale, ICIQ-UI SF, Kiefer Scale, Mental Health Component of the SF12V2-Health Survey (MCS-12) and three neuropsychological tests: Rey-Osterrieth complex figure test (ROCFT 30 min), auditory verbal learning test (AVLT I-V) and the NKP version of verbal fluency test. Seven patients needed more than one adjustment of the valve. This subgroup significantly improved only in Walking Score and Step Score but the trend was toward significant improvement in other variables. Eight patients had subdural effusions that were completely managed with adjustments until the 3-month control. BMI was significantly lower in patients with ≥2 adjustments compared to those with a maximum of one adjustment. Implantation had low complication rates and no mortality. Initial results are promising however more studies are needed to provide rationale for gravitational valves in iNPH. We recommend increasing the initial valve setting by 2–4 cm H2O above manufacturer’s recommendation, especially in lean patients.