Safety and Efficacy of a Deep Brain Stimulation System in Epilepsy: A Feasibility Study for Tracking Neural Excitability

The study is testing a new device that uses electrical stimulation of the brain for the treatment of epilepsy, The device is called the Medtronic Activa PC+S system. Two devices will be implanted per participant. The electrodes will be surgically implanted bilaterally into the hippopotamus and anterior nucleus of the thalamus, Participants that agree to be part of the study will be asked to remain in the study for a total of 2 years from the date of the device implantation. This will involve eight clinic visits: at 10 days post implantation, 2, 4, 6, 7, 8, 12 and 24 months post implantation. Each visit will last between 1.5-2 hours and will involve neurological examination by the participants doctor, all device calibrations will be conducted by the doctor and research team. The study coordinator or study doctor may also call participants to ask about seizure diary entries and participants can call the study coordinator/doctor at any time with questions or concerns. . At the end of the study the participant and their doctor can decide if they would like to have the device removed or if they would like to keep it in place. Participants can end participation in the study and have the device removed and any time for any reason, or for no reason. Surgical implantation will be conducted with participants under general anaesthesia. During the surgery, the doctor will make an incision in the scalp (less than 1 cm) and drill four holes (3 mm diameter) in the skull. The electrodes will be placed in the anterior nucleus of the thalamus and the hippocampus. The incision will be closed and the leads will be placed under the skin behind the ear, down each side of the neck and then to the Implantable pulse generators, placed under the skin, just below the collarbone. In the recovery phase (2 months) of the study we will collect 30 second EEG snapshots recorded every 15 minutes. Baseline phase: Following the recovery period data will continue to be recorded to establish baseline data, There is no stimulation during this period. We require a minimum number of five seizures to occur during this phase. Expected duration is 2 months, no longer than 3 months. If it takes longer than that then participation may be discontinued. Probing phase: Following the baseline phase, the devices will be used to electrically stimulate (probe) the thalamus continuously at a low frequency (2 Hz). EEG snapshots will continue to be collected. This period lasts for a minimum of 2 months and no longer than 3 months. We require at least 5 seizures that are well separated in time to have occurred to proceed to the next phase. Probe calibrated Deep Brain Stimulation (DBS) phase: In this phase we explore 18 DBS parameter configurations (three stimulus intensities; 3,4,5 Volts, six different frequencies; 125 130, 135, 140,145, 150 Hz) during two of the clinic visits. Each DBS parameter configuration will be tested for 1 minute with 4 minutes between each configuration test. The probing responses will be used to optimise the DBS parameters for each participant. This phase of the study continues for 2 months. The final phase of the study continues until the end of the study (2 years). During this phase the DBS parameters may be altered from the probing optimised parameters according to patient needs.