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

We recorded resting-state neuronal activity from the human subthalamic nucleus (STN) during functional stereotactic surgeries. By inserting up to five parallel microelectrodes for single- or multiunit recordings and applying statistical spike-sorting methods, we were able to isolate a total of 351 single units in 65 patients with Parkinson's disease (PD) and 33 single units in 9 patients suffering from essential tremor (ET). Among these were 93 pairs of simultaneously recorded neurons in PD and 17 in ET, which were detected either by the same (n = 30) or neighboring microelectrodes (n = 80). Essential tremor is a movement disorder without any known basal ganglia pathology and with normal dopaminergic brain function. By comparing the neuronal activity of the STN in patients suffering from PD and ET we intended to characterize, for the first time, changes of basal ganglia activity in the human disease state that had previously been described in animal models of Parkinson's disease. We found a significant increase in the mean firing rate of STN neurons in PD and a relatively larger fraction of neurons exhibiting burstlike activity compared with ET. The overall proportion of neurons exhibiting intrinsic oscillations or interneuronal synchronization as defined by significant spectral peaks in the auto- or cross-correlations functions did not differ between PD and ET when considering the entire frequency range of 1-100 Hz. The distribution of significant oscillations across the theta (1-8 Hz), alpha (8-12 Hz), beta (12-35 Hz), and gamma band (>35 Hz), however, was uneven in ET and PD, as indicated by a trend in Fisher's exact test (P = 0.05). Oscillations and pairwise synchronizations within the 12- to 35-Hz band were a unique feature of PD. Our results confirm the predictions of the rate model of Parkinson's disease. In addition, they emphasize abnormalities in the patterning and dynamics of neuronal discharges in the parkinsonian STN, which support current concepts of abnormal motor loop oscillations in Parkinson's disease.

Deep brain stimulation of the thalamus (thalamic DBS) is an established therapy for medically intractable essential tremor and tremor caused by multiple sclerosis. In both disorders, motor disability results from complex interaction between kinetic tremor and accompanying ataxia with voluntary movements. In clinical studies, the efficacy of thalamic DBS has been thoroughly assessed. However, the optimal anatomical target structure for neurostimulation is still debated and has never been analysed in conjunction with objective measurements of the different aspects of motor impairment. In 10 essential tremor and 11 multiple sclerosis patients, we analysed the effect of thalamic DBS through each contact of the quadripolar electrode on the contralateral tremor rating scale, accelerometry and kinematic measures of reach-to-grasp-movements. These measures were correlated with the anatomical position of the stimulating electrode in stereotactic space and in relation to nuclear boundaries derived from intraoperative microrecording. We found a significant impact of the stereotactic z-coordinate of stimulation contacts on the TRS, accelerometry total power and spatial deviation in the deceleration and target period of reach-to-grasp-movements. Most effective contacts clustered within the subthalamic area (STA) covering the posterior Zona incerta and prelemniscal radiation. Stimulation within this region led to a mean reduction of the lateralized tremor rating scale by 15.8 points which was significantly superior to stimulation within the thalamus (P < 0.05, student's t-test). STA stimulation resulted in reduction of the accelerometry total power by 99%, whereas stimulation at the ventral thalamic border (68%) or within the thalamus proper (2.5%) was significantly less effective (P < 0.01). Concomitantly, STA stimulation led to a significantly higher increase of tremor frequency and decrease in EMG synchronization compared to stimulation within the thalamus proper (P < 0.001). In reach-to-grasp movements, STA stimulation reduced the spatial variability of the movement path in the deceleration period by 28.9% and in the target period by 58.4%, whereas stimulation within the thalamus was again significantly less effective (P < 0.05), with a reduction in the deceleration period between 6.5 and 21.8% and in the target period between 1.2 and 11.3%. An analysis of the nuclear boundaries from intraoperative microrecording confirmed the anatomical impression that most effective electrodes were located within the STA. Our data demonstrate a profound effect of deep brain stimulation of the thalamic region on tremor and ataxia in essential tremor and tremor caused by multiple sclerosis. The better efficacy of stimulation within the STA compared to thalamus proper favours the concept of a modulation of cerebello-thalamic projections underlying the improvement of these symptoms.

We report on an unusual presentation of a task-specific focal oromandibular dystonia in a 47-year-old man of Turkish descent. His speech was affected exclusively while reciting Islamic prayers in Arabic language, which he otherwise did not speak.

Observed changes in spinal autogenic inhibition may allow measurement of the contribution of subcortical routes to the STN-HFS induced motor benefit in PD.