Chronic bilateral pallidal stimulation and levodopa do not improve gait inthe same way in Parkinson's disease: a study using video motion analysis system

Chronic bilateral internal globus pallidus (GPi) stimulation allows control of levodopa induced dyskinesias (LID) and motor symptoms in severe Parkins on's disease (PD). The effect on gait has not been clearly established. Dif ferent results have been reported, mostly consisting of clinical data. The aim of this study was to evaluate, by means of a video motion analysis syst em (optoelectronic VICON system), the influence of bilateral GPi stimulatio n on gait in PD. Five patients underwent bilateral GPi stimulation. The preoperative and pos toperative (3 months after surgery) clinical gait disturbances (items 29 an d 30 of the motor UPDRS), as well as spatial and temporal gait measurements (namely cadence, velocity, stride and step times, single and double limb s upport times, stride and step lengths) were analysed in off condition (the patient had received no treatment for 12 hours or merely the lowest dose of levodopa allowing him to walk for the gait analysis) and in the on drug co ndition (after administration of 200 mg of levodopa). The gait analysis was performed with the VICON system. In off condition, there was a statistically significant improvement after s urgery for UPDRS III and gait (clinically assessed). In on drug condition, there was a significant improvement for LID whereas UPDRS III and clinical assessment of gait were unchanged. The VICON system also showed that surgery improved gait especially in off c ondition, but also in on drug condition. Our method allowed exact quantification of the influence of surgery on gait characteristics. As compared with levodopa treatment, the effect of stimul ation seems to be different. Indeed, the results suggest only limited effec ts of pallidal stimulation on the control of stride length and rather point to compensatory additional mechanisms.