Abstracts

In the absence of intracerebral lesions, patients with refractory epilepsy are often scheduled for invasive video-EEG monitoring to localize the ictal onset zone during presurgical evaluation. Post-operative outcome is less favourable compared to patients with identified lesions such as hippocampal sclerosis. We evaluated the efficacy and safety of amygdalohippocampal (AH) deep brain stimulation (DBS) as a less invasive treatment alternative in these patients.
Seven patients (6M,1F) with refractory CPS and normal MRI were implanted with bilateral AH DBS electrodes and subdural grids and/or strips for localization purposes. In patients with ictal onset in the temporal lobe, AHDBS was initiated according to the side of ictal onset during a trial period with an external pulse generator. Patients with bilateral ictal onset were initiated with unilateral AHDBS if a predominant seizure onset side was found, otherwise bilateral AHDBS was planned. Patients with a significant reduction in interictal spikes and/or seizures during the initial trial period were implanted with an abdominally located pulse generator. Patients were followed-up at the epilepsy clinic every 2-4 weeks.
Two patients had a left-sided focal medial temporal lobe onset. Three patients had a right-sided regional medial temporal lobe onset. One patients had a bilateral regional onset with predominant involvement of the left temporal lobe. One patient had a left neocortical temporal lobe onset. 6/7 patients had a [gt] 50% reduction of interictal spikes during the initial AHDBS trial period. In one patient with very infrequent spiking, seizure frequency that had significantly decreased, was used as criteria. 6/7 patients were implanted with an internal generator. One patient has less than one month of follow-up and was not included in the long-term safety and efficacy analysis. The mean follow-up in the first 6 patients is 13 months (range: 4.5-20). One patient is seizure free for 1.5 years and had tapering of 2 AEDs. 3/6 have a [ge] 50% reduction in seizure frequency; 1/3 is seizure free during the day; 2/3 had tapering of 1 AED. 2/6 patients have a reduction of 25% of seizure frequency but had tapering of 2 AEDs; one of these patients had bilateral seizure onset and is currently being revised for bilateral AHDBS. In one patient no change in seizure frequency occurred. None of the patients reported side effects.
In this open pilot trial AHDBS significantly reduced seizure frequency during long-term follow-up without side effects. For patients who are less suitable candidates for epilepsy surgery, AHDBS may become a valuable alternative. Controlled studies in larger patient series are mandatory to identify the potential treatment population and optimal stimulation paradigms.
[Supported by: K. Vonck: FWO Junior Reseacher Grant. P. Boon: FWO grants 1.5236.99 and 6.0324.02 by BOF grants 01105399 and by the Clinical Epilepsy Grant 2002-2004. S. Dedeurwaerdere: BOF grant 011D9601 The implanted devices were provided by Medtronic.]