Hippocampal deep brain stimulation in nonlesional refractory mesial temporal lobe epilepsy

PURPOSE To evaluate the efficacy of chronic continuous hippocampal deep brain stimulation (DBS) in nonlesional refractory mesial temporal lobe epilepsy. METHODS Three adult patients with medically intractable epilepsy treated with hippocampal DBS were studied. Two patients underwent invasive recordings with depth stereo-electroencephalography (SEEG) electrodes to localize ictal onset zone prior to implantation of DBS electrodes. All the patients with no lesion in brain magnetic resonance imaging (MRI) scan received bilateral implantation of DBS electrodes. Chronic continuous high-frequency hippocampal stimulation was applied during treatment. The number of seizures in each patient before and after stimulation was compared. RESULTS Long-term hippocampal stimulation produced a median reduction in seizure frequency of 93%. Two out of these patients received unilateral activation of the electrodes and experienced a 95% and 92% reduction in seizure frequency after hippocampal DBS respectively. The last patient had bilateral electrode activation and had a seizure-frequency reduction of 91%. None of the patients had neuropsychological deterioration and showed side effects. Generalized tonic-clonic seizures disappeared completely after hippocampal DBS. CONCLUSIONS Chronic continuous hippocampal DBS demonstrated a potential efficiency and safety in nonlesional refractory mesial temporal lobe epilepsy and might represent an effective therapeutic option for these patients.