Upper extremity motor measures of Tap Test response in Normal Pressure Hydrocephalus

The Tap Test (TT) is a commonly used method for predicting shunt responsiveness in patients with Normal Pressure Hydrocephalus (NPH). The present study investigates whether measures of upper extremity motor function are useful for assessing response to spinal fluid drainage.

42 subjects undergoing evaluations for idiopathic NPH (iNPH) participated in this study. A standardized gait evaluation, a neuropsychological battery, and objective tests of upper extremity motor functions were administered. A Neurologist skilled in NPH assessment independently rated patients as TT Responders (n=26) or Non-Responders (n=16) based on clinical impression of change 2-4h after 40-50 cm(3) drainage of spinal fluid by lumbar puncture (LP). In the subset of subjects who underwent shunt placement, operative outcome was also evaluated.

TT Responders improved significantly more than TT Non-Responders in Upper Extremity Coordination/Speed tasks (p<.001). The groups did not differ on other neuropsychological measures post-LP. A possible association was observed between pre- and post-TT changes in Upper Extremity Coordination/Speed and post-shunt improvement. Among Upper Extremity Coordination/Speed measures, Line Tracing displayed the greatest sensitivity (76%) to change post-LP.

Our data suggest that measures of upper extremity motor functions may be useful as measures of Tap Test response in patients with iNPH. These upper extremity motor tasks can be rapidly administered (<5 min) in clinical practice and may provide an additional dimension beyond gait and cognition for evaluating response to LP.