Abstracts

Rationale: To investigate the efficacy and safety of electrical stimulation of the hippocampus in the treatment of patients with medically refractory mesial temporal lobe epilepsy. Methods: Five patients were included. All had refractory complex partial seizure, and some with secondary generalized. The patients underwent stereotactic implantation of quadripolar stimulating electrodes in hippocampus. Two patients received unilateral electrode implantation, while the other three received bilateral implantation. Stimulation of the hippocampal electrodes was turned ON immediately after the implantation of the internal programmable generator, with initial stimulation parameters: 1 V, 90-150 μs, 5 or 145 Hz. Seizures frequency was monitored and compared with pre-implantation baseline. Results: Five patients (two men and three women of complex partial seizure with or without secondary generalization) aged 27-61 year-old were studied with mean follow up period of 38 months (range, 29-43 months). The baseline seizure frequency was 2.0-15.3/month. The five patients demonstrated a substained effect of 45% (range 22-72%) seizure reduction to hippocampal stimulation. The two patients with the baseline seizure frequency of 2 per months have only achieved a 22-23% seizure reduction after hippocampal stimulation, whereas the remaining three patients with higher seizure frequency have more than 50% seizure reduction. There was no implantation or stimulation related side effect reported. Conclusions: Electrical stimulation of the hippocampus provides a non-lesional method that improves seizure outcome in medically refractory temporal lobe epilepsy. These experimental results prompt further controlled study in a large patient population and to evaluate the long-term effect of bilateral hippocampal stimulation.