STIMEP : Assessment of Subthalamic Nucleus Stimulation in Drug Resistant Epilepsy

The experimental work performed for more than 15 years by several research teams shows in animal models of epilepsy, that several circuits of basal ganglia are involved in the control of epilepsy seizures. The existence of those circuits leads to the possibility of therapeutic applications in particular deep brain stimulation. Preliminary results (Benabid et al, 2002) (Chabardes et al , 2002) suggest that the neuromodulation of basal ganglia and in particular the subthalamic nucleus and the substantia nigra pars reticulata could have a therapeutic effects in patients with drug resistant epilepsy and no possibility of resection surgery. This is a double blind, controlled and randomized clinical trial with two cross-over groups and four phases. Phase 1 : base line, open phase consisting of follow-up of patients with their standard treatment. Phase 2 : Randomisation, lead implantation, followed by 3 months wash out period with the stimulator switch OFF. Phase 3 : cross-over, double blind phase : 3 months with stimulator switch ON or OFF depending on randomization allocation, followed by 3 months with the stimulator switch on the opposite position. Phase 4 : open phase, one year follow-up of all patients with the stimulator switch ON. There are two differents groups at phase 3 : * Group A : 10 patients with the stimulator switch ON for three months and switch OFF for the next three months. * Group B : 10 patients with the opposite sequence, OFF and ON. Main objective : \- To show that high frequency deep brain stimulation of the subthalamic nucleus decrease the frequency of epileptic seizure compared with no stimulation. Secondary objectives : * To show that high frequency deep brain stimulation of the subthalamic nucleus improve the quality of life. * To describe the side effects of this device and compare with those described in Parkinson patients. In particular to check the onset of dyskinesia related to dopamine. * To compare the distribution of seizure frequency after stimulation to the base line. * To show that the number of patients responding to treatment are higher in the group with stimulator switch ON than in the group with the stimulator turn OFF. * To compare the number of days without seizure with the stimulator switch ON or OFF. * To evaluated the neuropsychologic effect induced by the neurostimulation * To quantify the types and the ratio of different seizures during the ON phase and the OFF phase. * To monitor the secondary drug use during the study. Control visits : all patients will have a control visit every 4 weeks during the study.