Cognitive changes following subthalamic nucleus stimulation in two patients with Parkinson disease.

The limits of a drug therapy in severe forms of Parkinson disease have led to refining neurosurgery on the basal ganglia. Deep brain stimulation of the subthalamic nucleus has been recognized as one of the most promising techniques to decrease "off" motor symptoms and motor fluctuations, allowing a reduction of drug therapy and limiting side effects of the drugs. There is still open debate on the possible consequences of chronic subthalamic stimulation in other ways, apart from motor symptoms, of general cognitive performance. We examined and followed two patients with Parkinson disease for 9 mo. after surgery for deep stimulation, studying their cognitive performances. There is a general amelioration of cognitive performances, in particular as far as linguistic capabilities is concerned. We discuss the possible significance of these results, reminding strenuously that only two patients were involved, so the potential for generalization is seriously limited.