Abstracts

We have previously studied the efficacy of amygdalohippocampal deep brain stimulation (AH-DBS) for temporal lobe epilepsy. The present study investigated the safety of AH-DBS in terms of cognitive functioning in patients with normal MRI findings. Eight consecutive patients (7M, 1F; 7 right-handed, 1 left-handed) with refractory CPS and normal MRI findings underwent AH-DBS on the side of temporal lobe ictal onset as defined by invasive video-EEG monitoring. Patients in whom a [gt]50% reduction of interictal spikes and/or seizures was shown during an initial trial period with an external generator, were implanted with an abdominally located pulse generator for long-term AH-DBS. Neuropsychological testing using a comprehensive test battery was performed before and after 6 months of AH-DBS. In 7/8 patients unilateral long-term AH-DBS was performed (left-sided: 4/7; right-sided: 3/7). All 7 stimulated patients were right-handed. After a mean follow-up of 22 months (range: 6-32 months) 2/7 patients had a [gt]90 % reduction in seizure frequency; 3/7 patients had a [gt]50 % seizure reduction; 2/7 patients are non-responders. One patient did not fulfil the long-term implantation criteria and underwent a temporal lobectomy. Before chronic DBS, the average number of AEDs was 3 (range 2-4). In 6/7 patients at least one AED was tapered. None of the patients reported side effects. In one patient an asymptomatic haemorrhage occurred on the amygdalar electrode trajectory, which resolved within one week. None of the patients showed changes in bedside neuropsychological testing. Formal neuropsychological assessment in 6/7 stimulated patients was unchanged in 3 patients, mildly improved in 2 patients and globally deteriorated in one patient. Additionally, a mild decrease of verbal memory was found in 3 patients of whom one was stimulated on the language-dominant side and already showed a pre-operative verbal memory deficit. This open pilot study shows a significantly decreased seizure frequency in the majority of patients treated with AH-DBS for refractory epilepsy without significant decreases in global neuropsychological functioning after 6 months of treatment. Whether AH-DBS interferes significantly with verbal memory, specifically in patients who are stimulated on the language dominant side, needs to be further investigated. (Supported by Senior Clinical Investigator Grant (PB), Junior Researcher ([ldquo]Aspirant[rdquo]) Grant (KV) and Grants 1.5236.99, B/02514 (PC) and 6.0324.02 from the Fund for Scientific Research (FWO)-Flanders; by Grant 01105399 from Ghent University Research Fund (B.O.F.) and by the Clinical Epilepsy Grant Ghent University Hospital 2000-2004.)