[Chronic intracerebral stimulation and abnormal movements: why and when? Major therapeutic advances in the 90s].

Surgical procedures for abnormal movements progressively evolved toward microinvasive techniques performed under stereotaxic control. The next advance was the development of well-tolerated intracerebral stimulation with reversible effects. The quality of the results depends on optimal definition of the stimulation target. Optimally, the surgical protocol includes stereotaxic ventriculography to identify targets followed by electrical activity recordings of the structures crossed by the electrode. Finally, a minute study of the stimulation effects is performed under sterotaxic control while the patient is awake. PARKINSON'S DISEASES: Indications for thalamic stimulation in Parkinson's disease have given way to subthalamic stimulation which improves tremor, bradykinesia and rigidity simultaneously. This result confirms the implication of the subthalamic nucleus in the pathogenesis of Parkinson syndromes. The palladium may be stimulated in Parkinson's patients with major iatrogenic involuntary movements. ESSENTIAL TREMOR: Thalamic stimulation is indicated for essential tremor. The efficacy of chronic stimulation is currently under evaluation in other indications.