Abstracts

Deep brain stimulation of different targets has recently been shown to be efficacious for refractory epilepsy. We have previously shown that chronic deep brain stimulation (DBS) electrodes are suitable for intracranial ictal onset localization in the medial temporal lobe. The purpose of the present study is to evaluate the efficacy and safety of long-term amygdalohippocampal (AH)-DBS in patients with normal MRI findings and temporal lobe epilepsy. Eight consecutive patients with refractory complex partial seizures (CPS) and normal MRI findings were implanted with bilateral AH-DBS electrodes and/or subdural grids for ictal onset localization and subsequent stimulation. In patients with ictal onset in the temporal lobe, AH-DBS was initiated according to the side of ictal onset during a trial period with an external pulse generator. Patients in whom [gt]50% reduction of interictal spikes and/or seizures was shown during the initial trial period were implanted with an abdominally located pulse generator. Prospectively, the frequency of CPS and side effects were carefully monitored, including bedside neuropsychological testing. Unilateral seizure onset in medial temporal lobe structures was found in 6/8 patients; in one patient a bilateral medial temporal lobe onset with unilateral preponderance was found; in another patient neocortical temporal lobe seizure onset was demonstrated.
In 7/8 patients unilateral long-term AH stimulation was performed. After a mean follow-up of 22 months (range: 6-32 months) 2/7 patients had [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. In 6/7 patients at least one AED could be tapered. None of the patients reported side effects. In one patient the amygdalar implantation was complicated by a minor and asymptomatic amygdalar haemorrhage, which resolved within one week. None of the patients showed changes in bedside neurological and neuropsychological testing. This open study demonstrates the efficacy of DBS in medial temporal lobe structures. More than half of the patients respond well to long-term AH-DBS. Assessment of side effects including neuropsychological functioning suggests that chronic AH-DBS is a safe treatment as well. (Supported by A Senior Clinical Investigator Grant (PB), a 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.)