Peripheral neuromodulation for drug-resistant epilepsy: the effect of short term transcutaneous trigeminal nerve stimulation on EEG activity

Aim: Trigeminal nerve stimulation (TNS) has been proven to exert beneficial effects on symptoms of drug-resistant epilepsy (DRE). However, whether and how TNS is able to modulate the electroencephalogram (EEG) background activity in DRE patients is still unknown. We aimed to investigate the effect of acute TNS on EEG activity by conducting qualitative (morphologic) and quantitative (power spectra) analyses on two groups of DRE patients, undergoing real or sham TNS.Methods: Twenty-two DRE patients were randomly divided into a “sham-TNS” or “real-TNS” group. Real-TNS was delivered bilaterally to the infraorbital nerve with trains of a symmetric biphasic square wave pulse (1 to 20 mA, 120 Hz), in a cyclic modality for 20 minutes. The sham-TNS protocol mimicked the real-TNS stimulation but at a zero intensity. EEG recordings were collected for each patient 10 minutespre, 20 minutesduringand 10 minutespostTNS delivery. EEG signal was subsequently visually analysed for interictal epileptiform discharge (IEDs) and processed by spectral analysis (Fast Fourier Transform). A between and within subject repeated-measures ANOVA was used for statistical analyses.Results: A significant increase of EEG absolute alpha power was observed in the during real-TNS compared to the sham-TNS (F2,18=1.748; p=0.006). Conversely, no significant effects were noticed either for quantitative analysis of other frequency bands or for IEDs detection.Conclusion: Short-term TNS is able to induce an acute effect on EEG background composition of DRE patients. In line with recent evidence, alpha rhythm enhancement might be interpreted as an index of functional inhibition, able to influence cortical activity and thus reduce seizure propensity.