Article abstract-Gait analysis was carried out to assess the effects of L-dopa and bilateral subthalamic nucleus stimulation on gait velocity, cadence, stride length, and gait kinematics in nine patients with PD. Substantial effects of bilateral subthalamic nucleus stimulation on gait, with an increase in gait velocity and stride length comparable to that of a suprathreshold L-dopa dose, were found. Interestingly, stride length was more improved by L-dopa and cadence more by subthalamic nucleus stimulation. In two patients with freezing during the "on" period, subthalamic nucleus stimulation failed to reduce this symptom effectively. The time needed to perform the stand-walk-sit test is also reduced. 1 Bilateral surgery or stimulation of either the internal pallidum (GPi) or the STN is required to improve axial symptoms such as the gait disorder in patients with PD.2,3 A quantitative study investigating the effects of STN stimulation on gait in patients with PD is lacking so far.After several years of treatment, freezing of gait may become resistant to L-dopa. 4 It has not been assessed whether L-dopa-resistant freezing may respond to STN stimulation. Because it has been proposed that preoperative L-dopa response predicts the clinical outcome after STN stimulation, 3 our interest was focused on patients who exhibited a gait disturbance with severe freezing even in their best "on" condition before surgery.Patients and methods. Nine patients with PD (mean age, 56 Ϯ 7 years; Hoehn and Yahr score, III to V) were studied 3 months after bilateral electrode implantation in the STN for deep brain stimulation (DBS). Seven patients had an L-dopa-responsive gait disorder (Group 1) and two patients were identified preoperatively as having severe freezing episodes, even at their best L-dopa response (Group 2). Ten age-matched, healthy subjects served as controls.The UPDRS and gait analysis were carried out following a 12-hour overnight withdrawal of dopaminergic medication. A subscale for gait was constructed (items 13 to 15 of part II and items 29 to 30 of part III of the UPDRS). Gait analysis was carried out under four different conditions: off drug and on stimulation, off drug and off stimulation, on drug and off stimulation, and on drug and on stimulation. For the on-drug condition, a suprathreshold dose of L-dopa was applied. Before gait analysis on a treadmill, the natural walking speed of each patient was measured during overground locomotion in each of the four conditions. Subsequently, a complete gait analysis was carried out on a treadmill, with the speed adjusted exactly to the subjects' individual gait velocities as measured before. Gait was recorded with a three-dimensional infrared movement analysis system, comprising four infrared cameras and video processors (50-Hz sampling rate) connected to a computer. Different gait measurements, including kinematics, were calculated using self-developed software. Results. After surgery, the UPDRS motor score was reduced by 45% with stimulation in the off-drug condition (G...

Deep-brain stimulation of the subthalamic nucleus appears to reduce levodopa-induced dyskinesias, but whether this effect is caused by the reduction of the total levodopa ingestion or represents a direct effect on the motor system is unknown. Precision grip force of grasping movements and levodopa-induced dyskinesias was analyzed in 10 parkinsonian patients before and after 3 months of deep-brain stimulation of the subthalamic nucleus. Peak grip force was abnormally increased before surgery in the off-drug state and, particularly, in the on-drug state (sensitization). This grip force upregulation normalized with chronic deep-brain stimulation in both conditions (desensitization). Peak-dose dyskinesias also improved, and off-dystonia was completely abolished. Mean dosage of dopaminergic drugs was reduced, but force overflow and dyskinesias were equally improved in 2 patients without a reduction. Despite the same single levodopa test dose, force excess and levodopa-induced dyskinesias were drastically reduced after 3 months of deep-brain stimulation of the subthalamic nucleus. This indicates that direct effects of deep-brain stimulation of the subthalamic nucleus on levodopa-induced dyskinesias are likely to occur. Grip force overflow is a promising parameter to study the desensitizing effect of chronic deep-brain stimulation on levodopa-induced dyskinesias.

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