GAIT INITIATION IN PARKINSONS-DISEASE

We studied the kinematic patterns of gait initiation in 31 patients wi th Parkinson's disease and in 20 age-and sex-matched normals by using an optoelectronic tracking system (ELITE). Position markers were attac hed to the skin overlying the ankle, knee, hip, elbow, shoulder, and z ygomatic bone. Subjects were instructed to start walking immediately a fter an acoustic go signal. Gait initiation was defined as the phase b etween standing motionless and steady-state locomotion. This phase was subdivided into a movement preparation period (the time between go si gnal and movement onset) and a movement execution period (the time bet ween movement onset and the end of the first stride). Onset and durati on of ankle, knee, hip, trunk, and arm motion within the first stride were analyzed. Movement preparation time was significantly increased i n Parkinson's disease (p = 0.01), whereas movement execution times wer e similar in both groups (p = 0.23). Initiation of ankle, knee, hip, a rm, and trunk movements was delayed in patients as compared with healt hy subjects, but the relative timing and the sequence of submovements was comparable in both groups, indicating that the overall pattern of submovements was preserved in the patients. Our data suggest that gait initiation deficits in Parkinson's disease cannot be explained by a d isordered sequence of limb and hunk submovements. More likely, gait in itiation problems originate from the basal ganglia's internal cueing d eficit for movement sequences, delaying onset and slowing the executio n of all subcomponents.