Safety and Efficacy of Motor Cortex Stimulation in the Treatment of Advanced Parkinson Disease

Advanced stage of Parkinson disease (PD) is a difficult condition to treat, especially after several years of dopaminergic drugs. Recent development of neurosurgical techniques using deep brain stimulation leads has shown good behavioral results in these advanced PD patients. However, the placement of a stimulation lead in the subthalamic nucleus is a complex, invasive, and long surgical procedure. Such intervention requires a sophisticated technical environment, including a stereotactic magnetic resonance imaging (MRI) exam, associated with per-operative electrophysiological exploration of deep brain structures. This surgical treatment can therefore be indicated only for a few selected patients, and cannot be offered to a large proportion of patients among the potential candidates (estimation of 5000 patients in France). Thus, there is a need to develop therapeutic alternatives that would be technically and practically more convenient, less invasive, and that could be offered to a larger number of patients. Several clinical studies, including one led by our group, have already demonstrated that transcranial magnetic cortical stimulation could improve bradykinesia and shorten motor reaction time in patients with Parkinson disease. The clinical benefit was however moderate, and transient, probably because the stimulating sessions were too short in duration. A prolonged effect could be obtained with continuous cortical stimulation. Such cortical stimulation has already been developed with good clinical tolerance in our hospital since 1991 for chronic neuropathic pain syndromes. In a non-human primate model of late stage Parkinson disease, we have recently demonstrated that prolonged primary motor cortex stimulation significantly improved both akinesia and bradykinesia. The primary objective of this pilot study will be to evaluate the tolerance and efficacy of chronic stimulation of the primary motor cortex in 10 patients suffering from advanced stage Parkinson disease, despite the optimisation of dopaminergic treatment. The expected benefit for the patient will be gait improvement, increased movement velocities, and finally a better quality of life associated with reduction in dopaminergic medication and low per-operative morbidity risk.