Effect of vagal nerve stimulation on patients with bilateral temporal lobe epilepsy

Objective: To investigate the effects of vagus nerve stimulation (VNS) on the seizure frequency in patients with drug-resistant epilepsy (DRE) and bilateral temporal lobe epilepsy (bi-TLE). Additionally, we aimed to determine the safety of VNS and its side effects.

Methods: Our retrospective study included 17 patients with bi-TLE who underwent VNS-device implantation at our center from 1997 to 2019. The main outcome was a reduction in seizure frequency. Bitemporal cases were confirmed using scalp electroencephalography (EEG) or invasive electroencephalography (iEEG).

Results: The median age at seizure onset was 18 years. Bi-TLE was confirmed by scalp EEG in 47 % and by iEEG in 53 % of the patients. The median follow-up period was 36 months. The median seizure frequency per month before and after VNS was 9.5 (IQR = 4.3-35.3) and 2 (IQR = 0.8-4.2), respectively. Compared to baseline, 70.5 % of the patients achieved ≥ 50 % reduction in seizure frequency, whereas 35.3 % experienced either no or minimal reduction in seizure frequency. The response rate (>50 % reduction in seizure frequency) was 87.5 % in patients who underwent scalp EEG and 55.5 % in those who underwent iEEG. For VNS treatment, the median follow-up was at 36 months (IQR = 17-46.5). Adverse effects were observed in 59 % of the patients, including cough and hoarseness.

Discussion: Therapeutic choices are limited in cases of drug-resistant bi-TLE. Our study on VNS-device implantation in bi-TLE suggests a positive outcome.