Effects of CSF tap test on the gait disturbance in normal pressure hydrocephalus

In normal pressure hydrocephalus (NPH) a disturbance of gait is typically the first symptom to appear and is considered as most important within the symptomatic triad described by Hakim and Adams. The most common test for the outcome of a shunt operation is a CSF tap test. In this study we investigated which gait parameters positively response to CSF tapping and at which time period after tapping this response is most pronounced. The study cohort comprised 41 patients (72.2±10.0 years, 12 females). All patients underwent a cranial MRI scan prior to CSF tap test, a neuropsychological examination prior and after CSF tapping and a gait analysis prior and immediately, 12h and 48–96h after CSF tapping. Gait analysis was performed on a pressure-sensitive gait carpet (GaitRITE®). Patients were tested under two different speed-, two cognitive dual-task- and one motor dual-task-condition. All standard temporal and spatial gait cycle parameters were analyzed. Positive effects of CSF tapping on the gait performance were most pronounced during walking with preferred walking speed. Patients did also show improvements while walking with maximal speed and for the motor dual-task but not for the two cognitive dual task conditions. Velocity, stride length, stride time and double support time were the parameters that responded most positively (p<0.01). In nearly all cases improvements were detectable not till 12h or even 48h after the CSF tapping. These results indicate that in contrast to the commonly assessed maximal walking velocity, a multi-parametric analysis of the preferred walking pattern might have a more precise predictive value for the outcome of a shunt operation. In addition, gait examinations immediately after the CSF tap test will overlook most gait improvements and therefore gait assessments to later time points are necessary to detect all positive effects on the walking performance.

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