[Physiopathology of parkinsonism and dyskinesias: lessons from surgical observations]]

Current models about the organization of the basal ganglia have provided a resurgence of the surgical treatment of Parkinson's disease (PD). Surgical experience has served to corroborate many of the predictions supported by the model. For instance, hyperactivity of the subthalamopallidal pathway is the key feature in PD and its suppression is associated with an improvement of the cardinal signs and symptoms of the disease. Parkinsonian rest tremor may be related to the oscillatory activity of the subthalamic and pallidal neurons. However, some clinical observations can not be entirely explained by the model. The most important paradox is the disappearance of levodopa-induced dyskinesias after pallidal surgery. This review critically analyzes the validity of the current model based on the surgical observations.