Broadening a classic clinical triad: The hypokinetic motor disorder of normal pressure hydrocephalus also affects the hand

The clinical spectrum of normal pressure hydrocephalus is thought to comprise the triad of hypokinetic gait disorder, dementia and urinary incontinence. In contrast, motor abnormalities involving the upper limbs in normal pressure hydrocephalus have not yet received a great deal of attention. The present study was designed to quantitatively assess grasping movements in normal pressure hydrocephalus and to compare the performance with that in Parkinson's disease. Eight subjects with normal pressure hydrocephalus, eight subjects with Parkinson's disease and eight healthy control subjects grasped to lift an instrumented object. The built-up of fingertip forces during the early phase and the kinematics of the lifting movement during the late phase of the grip–lift synergy were slower for patients compared to healthy controls. Patients generated abnormally high fingertip forces when lifting and holding the object stationary. The slowness of the grip–lift synergy and the force overshoot was similar for both patient groups. Our data demonstrate that the hypokinetic motor deficit in normal pressure hydrocephalus also involves the hand, and that the pattern of deficits shares several features of those found in Parkinson's disease.