Single cell activity recorded in the subthalamic nucleus (STN) of Parkinson's patients and the effect of tremor, passive and voluntary movement upon the same cells are described. Three types of cells were distinguished by the pattern of discharge: tonic, phasic and rhythmic. They all demonstrated high mean firing rates (65, 59 and 69 Hz, respectively). Simultaneous recordings of muscle activity and tremor helped in defining cell activity. The implantation of the definitive stimulating electrode in the patients was based on the number of STN cells related to tremor, active and passive movements (mean = 68%) along the track chosen. Cells were related to tremor (n = 21; 11%), modified the discharge with differences in the amplitude of tremor (n = 4), and changed the rate and pattern when tremor stopped spontaneously or artificially (n = 6). Movement-related cells (n = 97; 51%) showed a cyclic activity correlated with phases of the movement, or modified the firing rate along the performance of the movement. Tremor and movement-related cells (n = 11; 6%) revealed an interesting sensory-motor integrative function.

Twenty-two patients with Parkinson's disease were treated by implanting electrodes in the subthalamic nucleus. The follow-up evaluation was conducted at one (22 patients) and two years (9 patients). Significant improvement in the Unified PD Rating Scale scores was found. Tremor diminished 100% in the on drug/on stimulation and 70% off drug/on stimulation state. Rigidity decreased by 68% in the on drug/on stimulation and by 52% in off drug/on stimulation state. Subthalamic stimulation is reliable.

No abstract