Sustained Effect 1 Month After CSF Tap Test in Normal Pressure Hydrocephalus

Background The response to CSF tap test (TT) has been considered an indicator of normal pressure hydrocephalus (NPH) and a predictor of shunt effectiveness. Although the effects of the CSF TT are thought to be transient, the duration of those effects has not been studied in detail. Method We performed a retrospective analysis of 32 consecutive patients with NPH who underwent quantitative gait analysis before, immediately after, and 1 month after the CSF TT. Responses to the TT were defined as a 15% or greater improvements in step length or walking speed. Result Immediately after the CSF TT, 24 of 32 patients showed a response on step length or walking speed. Among the 24 patients with a response immediately after the TT, a sustained response 1 month after the TT was maintained in 16 patients. Furthermore, among the 8 patients without an immediate response, 5 patients showed a delayed response 1 month after TT. Conclusion The effects of the CSF TT on gait parameters were sustained for 1 month in approximately half of the patients with NPH. Decreased tensile strength of the ventricular wall after the TT might explain the sustained effects.