Cognitive impairment predicts worse short-term response to spinal tap test in normal pressure hydrocephalus.

Introduction: In patients with idiopathic normal pressure hydrocephalus (iNPH), the spinal tap test (STT) is commonly used to predict ventriculoperitoneal shunt responsiveness. Clinical improvement following STT usually is measured by testing gait function. In our study, we investigated the impact of cognitive impairment on gait improvement after STT.

Methods: 22 patients with the clinical and radiological diagnosis of iNPH underwent gait analyses (mobile measuring system Medilogic) before and 2-4h after STT in self-paced gait velocity over 7m. Prior to STT, cognition was evaluated by the Mini Mental State Examination (MMSE). MMSE<24/30 points was used to define the subgroup of patients with cognitive impairment (iNPH-CI). Spatio-temporal parameters of gait before STT vs. after STT were analyzed with ANOVA with repeated measures.

Results: 1. Baseline gait parameters did not differ between the two groups: patients with iNPH and normal cognition (n=11) and patients with iNPH-CI (n=11). 2. Following STT, there was significant improvement of gait parameters in patients without cognitive impairment, while patients with iNPH-CI did not benefit from STT.

Conclusion: Subjects with iNPH have a higher probability of lack of gait improvement 2-4h following STT, if cognitive impairment is present. Further studies are needed to elucidate the associations of cognitive impairment and quantitative gait parameters measured early and at later time points after STT.