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Introduction: Deep brain stimulation (DBS) is a widely accepted clinical technique. The main motor symptoms are significantly reduced. The success of the technique depends on the experience of the neurosurgeon, neurologist and neurophysiologist who carry it out. The presentation of extensive series is needed to confirm and further currently held knowledge., Aim: To demonstrate the clinical benefits of a long series of patients treated by a single group with a minimum follow-up of one year and to report new neurophysiological data., Patients and Methods: The study examined a total of 250 patients with different diagnoses: most of them with Parkinson's disease, tremor and dystonia. The nuclei that were chosen were located by magnetic resonance imaging, computerised axial tomography and neurophysiological registers. Neurophysiological exclusion criteria, such as reflex control of heart rate, sympathetic skin response and auditory startle reflex, are employed in order to exclude patients with Parkinson-plus., Results: The motor sub-scale (part III) of the Unified Parkinson's Disease Rating Scale improves by 64% in the off-medication status with sub-thalamic stimulation at one year after surgery. One year after DBS, patients with dystonia show a significant decrease on the Burke-Fahn-Marsden dystonia scale. The improvement on the scales continues, with a mean descent of 65% in the second year after surgery., Conclusions: DBS is a suitable technique for the treatment of movement disorders. The neuronal activity of the sub-thalamus and the internal globus pallidus presents its own characteristics that reflect the motor symptoms of the patients. Surface electromyography proves to be useful for quantifying the patients' improvement.

Deep brain stimulation (DBS) was applied in the internal segment of the globus pallidus (GPi) to treat dystonia in 10 patients. One year after surgery the Burke-Fahn-Marsden movement scores were significantly lower than preoperative values (P=0.01). Two years after surgery the mean decrease reached 65% (P=0.001) with no motor symptoms worsening. Single unity activity was recorded in the operating room: GPi cells discharged with tonic (n=19; 29%), irregular (n=32; 48%), or burst-like activity (n=15; 23%) and fired with a mean discharge rate of 39 Hz+/-22. Some neurons demonstrated an oscillatory activity with periods lasting several seconds. Pairs of pallidal cells (n=8) recorded simultaneously displayed discharge synchronization. Movement modulated 64.4% of the cells tested, with increases in firing in 89% of cells and decreases in firing in 10% of cells. GPi cells responded to flexion and extension movements and to several passive manipulations indicating an important sensory role in dystonia. GPi neurons fired in advance of the electromyography (EMG) when the surface EMG was recorded simultaneously with the neuronal activity. Spectral analysis of the co-contracting muscles during dystonia demonstrated prominent high peaks at a low frequency band (20 Hz) during involuntary and voluntary movements. The high amplitude EMG profile recorded at rest diminished to very low values with GPi stimulation, allowing an ease of voluntary contractions. We conclude that DBS in the GPi is a reliable surgical technique for dystonia. GPi cells discharge with distinct electrophysiological characteristics that may explain some of the symptoms in dystonia. EMG recording in the operating room helps to determine which DBS contacts produce the best benefit.

Introduction: Subthalamic nucleus stimulation (SNE) is currently a reasonable treatment for patients with advanced Parkinson's disease (PD). Predictive factors for effective SNE have not yet been identified with precision. We have prospectively evaluated response to SNE in a series of patients with advanced PD to study the factors that influence clinical improvement after functional surgery., Methods: We prospectively studied 20 patients with advanced PD (age: 59 +/-6.1; stage: 3.0+/-0.8) candidates for SNE. We studied these patients preoperatively and 6 months postoperatively according to Core Assessment Program for Intracerebral Transplantation (CAPIT) protocol including timed tests., Conclusions: We found a negative correlation between age and Unified Parkinson Disease Rating Scale (UPDRS) improvement; however, age did not correlate with timed tests improvement. In addition, preoperative severity (UPDRS and Hoehn-Yahr) did not correlate with UPDRS and timed tests improvement. In summary, age is a negative predictor for effective SNE.

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.

Introduction: The subthalamic nucleus has been demonstrated to be involved in Parkinson's disease. Electrical stimulation of this nucleus at high frequency was proved to revert most symptoms and is used as the most advanced alternative therapy. The technique requires the recording of single cell activity as an important step in locating spatially the limits of the nucleus together with magnetic resonance imaging and ventriculography., Objectives: To study the electrophysiological properties of single cells in the subthalamus. This information is important to recognize the nucleus in the operating room so as to implant the definitive stimulating electrode., Patients and Methods: Twelve patients with Parkinson's disease were implanted with bilateral electrodes in the subthalamic nucleus. Several neurological tests were applied during one year to study the clinical results., Results: Single cell activity was recorded in both hemispheres. Three types of cells were recognized based on the mode of discharge: tonic, phasic and rhythmic. The track chosen to implant the definitive electrode was based on the higher number of cells recorded and on the response to tremor and passive or voluntary movements. The neurological tests applied demonstrated a diminution of the symptoms., Conclusion: The subthalamic nucleus plays an important role in handling motor and sensory information. Stimulation of the nucleus at high frequency reveals an amelioration of Parkinson's symptoms during the one year period of study.

Extracellular cell activity was recorded in the intermediate and posterior subdivisions of the nucleus basalis of Meynert (NBM) of awake monkeys to determine cell characteristics and the motor and sensory participation. Animals were trained to move a lever by elbow flexion-extensions to receive a reward. Cell activity was recorded when the animal was at rest and executing the task. The electromyogram of the upper limb, contralateral to the recording site, was recorded simultaneously with NBM neuron activity. The effect of visual, auditory, and tactile stimuli were also studied after performance of the learned task. A moderate number of cells responded to the reward (16%), while a higher percentage of them was associated with unexpected, unspecific stimuli (22%). Firing rates correlated positively with limb movement (30%). Visual (34%) and auditory (15%) responses were also found. No NBM cell responded to tactile stimulation. Considering these findings and the anatomical projections over the cortex, the NBM role ion complex integrative processes in discussed.

Responses of substantia nigra (SN) pars compacta (SNc) and reticulata (SNr) neurons to sensory stimulation and movement were investigated in awake Macaca fascicularis. Concern was assigned to polysensory and sensory/motor convergence on the same cell, which were found in 12% and 9% of the neurons, respectively. Others were modality specific (35%) or unresponsive (44%). The convergence lends support to the notion that SN plays an important role in sensory-motor integration.

Single cell activity was recorded in the pars compacta (SNc) and pars reticulata (SNr) of the substantia nigra (SN) in 4 unanesthetized Macaca fascicularis to determine the motor role of the nucleus. Animals were trained to perform a simple task that involved moving a lever by elbow flexion-extensions, in the horizontal plane using the hand contralateral to the recording site. Two monkeys learnt to execute the task on both sides. Electromyograms (EMG) of limb muscles were recorded simultaneously with SN neurons. Discharge rate modulation related to specific movement phases was present in 35% of the neurons. A significant positive correlation of the discharge rate with movement velocity and amplitude was found in SNc and SNr neurons. Some SNr cells discharged in anticipation of the EMG, suggesting a participation of the nucleus in the preparation of movement. The activity of SNr neurons was also related to movement of the left and right upper limb. In conclusion, the SN seems to play an important role in the control of specific motor mechanisms, probably modulating movement velocity, amplitude and direction, with little participation of somatosensory feedback. The involvement of the SNr in the coordination of bilateral arm activity is discussed.