We studied 48 patients after bilateral subthalamic nucleus deep brain stimulation (STN‐DBS) who were evaluated 6 months after the surgical procedure using the Unified Parkinson's Disease Rating Scale (UPDRS) in a standardized levodopa test. Additional follow‐up was available in 32 patients after 12 months and in 20 patients after 24 months. At 6 months follow‐up, STN‐DBS reduced the UPDRS motor score by 50.9% compared to baseline. This improvement remained constant at 12 months with 57.5% and at 24 months with 57.3%. Relevant side effects after STN‐DBS included intraoperative subdural hematoma without neurological sequelae (n = 1), minor intracerebral bleeding with slight transient hemiparesis (n = 1), dislocation of impulse generator (n = 2), transient perioperative confusional symptoms (n = 7), psychotic symptoms (n = 2), depression (n = 5), hypomanic behaviour (n = 2), and transient manic psychosis (n = 1). One patient died because of heart failure during the first postoperative year. The current series demonstrates efficacy and safety of STN‐DBS beyond the first year after surgical procedure. Complications of STN‐DBS comprise a wide range of psychiatric adverse events which, however, were temporary. © 2003 Movement Disorder Society

The optimal stimulation site in subthalamic deep brain stimulation (STN-DBS) was evaluated by correlation of the stereotactic position of the stimulation electrode with the electrophysiologically specified dorsal STN border. In a series of 25 electrodes, best clinical results with least energy consumption were found in contacts located in the dorsolateral border zone, whereas contacts within the subthalamic white matter, e.g., zona incerta, were significantly less effective. We suggest that the dorsolateral STN border should be covered by STN-DBS.

Deep brain stimulation of the subthalamic nucleus (STN–DBS) is an established therapy for Parkinson's disease (PD). A manic episode with psychotic symptoms induced by STN–DBS occurred in a previously psychiatrically healthy patient, focusing on the role of STN–DBS in influencing not only motor but also emotional behaviour. © 2003 Movement Disorder Society

Background: The subthalamic nucleus is the preferred target for deep brain stimulation in patients with advanced Parkinson's disease. The site of permanent stimulation is the subject of ongoing debate, as stimulation both within and adjacent to the subthalamic nucleus may be effective. Objective: To assess the position of active electrode contacts in relation to the dorsal margin of the subthalamic nucleus as determined by intraoperative microrecordings and magnetic resonance imaging (MRI). Methods: In 25 patients suffering from severe levodopa sensitive parkinsonism, deep brain stimulating electrodes (n = 49) were implanted following mapping of the subthalamic nucleus by microrecording and microstimulation along five parallel tracks. Postoperative stereotactic radiography and fusion of pre-and postoperative MRI studies were used to determine the stereotactic position relative to the midcommissural point of the most effective electrode contacts selected for permanent stimulation (n = 49). Intraoperative microrecordings were analysed retrospectively to define the dorsal margin of the subthalamic nucleus. In cases where the dorsal margin could be defined in at least three microrecording tracks (n = 37) it was correlated with the position of the active contact using an algorithm developed for direct three dimensional comparisons. Results: Stimulation of the subthalamic nucleus resulted in marked improvement in levodopa sensitive parkinsonian symptoms and levodopa induced dyskinesias, with significant improvement in UPDRS III scores. In several instances, projection of the electrode artefacts onto the T2 weighted MRI visualised subthalamic nucleus of individual patients suggested that the electrodes had passed through the subthalamic nucleus. When the actual position of active electrode contacts (n = 35) was correlated with the dorsal margin of the subthalamic nucleus as defined neurophysiologically, most contacts were located either in proximity (± 1.0 mm) to the dorsal border of the subthalamic nucleus (32.4%) or further dorsal within the subthalamic region (37.8%). The other active contacts (29.7%) were detected within the dorsal (sensorimotor) subthalamic nucleus. The average position of all active contacts (n = 49) was 12.8 mm (± 1.0) lateral, 1.9 mm (± 1.4) posterior, and 1.6 mm (± 2.1) ventral to the midcommissural point. Conclusions: Subthalamic nucleus stimulation appears to be most effective in the border area between the upper subthalamic nucleus (sensorimotor part) and the subthalamic area containing the zona incerta, fields of Forel, and subthalamic nucleus projections.

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...