Abstracts

Rationale: Deep brain stimulation (DBS) of different intracerebral targets as a treatment for refractory epilepsy is under investigation in several clinical trials. The purpose of the present study is to report on the extended follow-up of patients with MTL epilepsy who underwent chronic DBS in medial temporal lobe (MTL) structures. Methods: 11 consecutive patients (8M) with refractory MTL CPS /-SG underwent uni-or bilateral MTL DBS depending on seizure onset localisation as determined by invasive video-EEG monitoring. When unilateral MTL DBS failed to decrease seizures with >90% after at least 2 years of stimulation, a switch to bilateral MTL DBS was proposed. Results: After a mean follow-up of 7 years (range: 52 -105 months), 3/11 patients are seizure free for >12 months. 3/11 patient have a >90 % reduction in seizure frequency; 3/11 patients have a reduction in seizure frequency of 50 %; 1/11 patient has a reduction in seizure frequency of 30-50%; one patient is a non-responder. The mean output current is 1.9V (range: 0-3.1). In 1 seizure free patient unilateral DBS was interrupted after 48 months due to seizure freedom with continued seizure control at maximum follow-up. In all patients (4/11) with a focal unilateral ictal onset a >90% seizure frequency reduction is found. In 2/5 patients with a regional unilateral ictal onset, a >90% seizure frequency reduction is found. In all patients (2/11) with bilateral ictal onset a <50% seizure frequency reduction is found. 9 patients were initiated on unilateral MTL DBS. In 5/6 in whom DBS failed to decrease seizures with >90%, bilateral DBS was started resulting in improved seizure control in 2/5 patients and seizure freedom in 1/5. None of the patients reported side effects. One patient had asymptomatic intracranial haemorrhages along the insertion of the deep brain electrodes. In one patient a cable revision was performed. In one patient bilateral DBS was switched to unilateral DBS due to acute seizure induction upon output increase trials. Mean number of AEDs before and after DBS is 3. Conclusions: This open study with an extended long-term follow-up demonstrates maintained efficacy of DBS in MTL structures. In >50% of patients, a seizure frequency reduction of at least 90% is reached. 25% of patients become seizure free.