Abstracts

Rationale: For medically refractory focal epilepsy, deep brain stimulation (DBS) of the anterior nucleus of the thalamus (ANT) has become an established therapeutic strategy in Europe. Also, DBS of the Ncl. accumbens (NAC) has been shown to be safe and potentially efficacious (Schmitt and Voges et al. Journal of Neurology 2014). However, little is known about the electrophysiological consequences of DBS for both targets, partly because of the lack of appropriate data aquisation. Methods: We had the opportunity to analyze frequency and location of interictal discharges of five patients treated with NAC-DBS and subsequently three patients with NAC-DBS and NAC-ANT-DBS during a seven day period of long-term monitoring video-eeg-monitoring. These results were compared to baseline before DBS initiation and to seizure outcome after 6 months of chronic DBS. Results: Reduction in IEDs frequency was not significant and did not correlate with a seizure reduction in 6-months period (defined as 50% seizure reduction compared with 3-month-baseline period). In two patients (both non-responders in 6-month period) showed a change in IED localisation: one patient with frontal lobe epilepsy had a relative increase in temporal IEDs after ANT-DBS and one patient with temporal lobe epilepsy a relative increase in right temporal IEDs after NAC-DBS. During ANT-NAC-DBS there was no change in IED frequency, IED localisation or 6-month period seizure outcome compared to baseline, NAC-DBS or ANT-DBS. Conclusions: DBS changes the irritative zone independent from the location of the epileptogenic zone and of response to this treatment modality. ANT-DBS does not add additional benefit to NAC-DBS responders. Further analysis with higher number of patients are necessary to support these preliminary findings.