Influence of pallidal stimulation and levodopa on gait and preparatory postural adjustments in Parkinson's disease.

In order to assess the influence of the bilateral internal globus pallidus (GPi) stimulation on gait and postural instability in Parkinson's disease (PD), we compared gait kinematic parameters and preparatory postural adjustments before and 3 months after stimulation in off- and on-drug conditions for seven patients. Gait kinematic parameters and displacements of centre of pressure (CP) and shoulder computed before a lateral raising task of the leg, were recorded using optoelectric Vicon system. Levodopa (L-dopa) induced a clear benefit for gait velocity (related to an increase of stride length) and also an increase of swing phase duration. GPi stimulation had a limited effect, since the increase of gait velocity was induced by a concomitant increase of stride length and cadence corresponding to a compensatory mechanism. The benefit on swing phase duration was also moderate. Displacements of CP were improved mainly by L-dopa. GPi stimulation and L-dopa had the same beneficial effect on the speed at which the CP was transferred back towards the support side, the ankle velocity, the onset time for ankle displacement, and the decrease of shoulder amplitude towards the support side, which reflects a better postural adjustment phase. This study, based on an objective method, revealed that chronic bilateral GPi stimulation may improve gait and preparatory postural adjustments in severe PD patients with a more limited effect than L-dopa. Copyright 2001 Movement Disorder Society.