Abstracts

Rationale: Hippocampal DBS has been increasingly used in the treatment of patients with temporal lobe epilepsy. Therapeutic electrodes are inserted using a longitudinal approach, using an occipital entry point. We report on the targeting accuracy in this patient population. Methods: Eighteen patients with refractory temporal lobe epilepsy submitted to hippocampal DBS were studied. Ten patients had unilateral mesial temporal sclerosis, 4 had bilateral mesial temporal sclerosis, 3 had normal MRI and 1 had bilateral periventricular nodular heterotopia. Nine patients were submitted to unilateral and 9 to bilateral hippocampal DBS. There were 27 electrodes, comprising 108 contacts. All were submitted to hippocampal quadripolar lead (Medtronic 3391) insertion using a posterior longitudinal approach through an occipital burr hole. A postoperative MRI documented the final position of each contact. Results: All contacts were located either in the hippocampus itself or its immediate vicinity. In 10 patients, all contacts were located inside the hippocampus proper; 6 patients had 3 contacts within the hippocampus and 6 patients had 2 contacts within the hippocampus. Among the contacts located within the hippocampus, 25 contacts were in the central hippocampus, 21 were in the superior hippocampus, 13 in the inferior hippocampus and 28 in the lateral portion of the hippocampus. One patient had contacts in the parahippocampus immediately inferior to the hippocampus; 18 contacts were located inside the temporal horn, immediately lateral to the hippocampus. Conclusions: The longitudinal approach was effective in adequately placing the electrode`s contacts within the hippocampus in patients submitted to hippocampal DBS. The accuracy in this series was superior to that reported in a close loop DBS cohort, in which up to 50% of the contacts were located outside the hippocampus. Funding: None