Laryngeal Motor Evoked-potentials as a Biomarker of Vagus Nerve Stimulation in Epileptic Patients (NEURO-LARYNX)

The goal of this study is to record and characterize larynx evoked motor potentials induced by vagus nerve stimulation. This study will include 10 adult patients implanted with a Vagus nerve stimulator, followed at the Center for Refractory Epilepsy at Cliniques St Luc. The inclusion criteria are: (1) patient aged between 18 and 65 years ; (2) cervical VNS device (Cyberonics, Houston, TX, USA) implanted for at least 6 months, (3) normal electrode impedance of the electrode. Exclusion criteria are (1) presence of a concomitant laryngeal pathology or recurrent laryngeal nerve damage, independent from VNS ; (2) important VNS side effects reported by the patient, such as severe dyspnea (grade III-IV) or severe pain in the neck/ear region.

Patients participating will be asked to come to the Neurophysiology Department of Saint Luc Clinic to peform the laryngeal evoked motor potential.

All patients belong to the refractory epilepsy group. Intervention: Characterization of Vagus nerve stimulation: Evoked potentials (EP) are recorded using an EEG/EP digital acquisition system

Characterization of Vagus nerve stimulation induced larynx evoked motor potential. Patients participating in the study will be asked to come to perform the experiment (duration maximum 1 hour) at the Neurophysiology Department of Saint Luc .

Characteristics of the laryngeal motor evoked potential Threshold : the mA of current output necessary for evoking the LMEP Latency : the time between the negative peak of the stimulation artifact and the first positive deflection of the LMEP Amplitude : the difference in μV between the lowest negative and the highest positive peak of the LMEP Duration : the time between the first positive deflection of LMEP and the return to the noise level Dose- response curve: the relation between increasing intensity of vagal nerve stimulation and amplitude of the LMEP

the LMEP is recorded for 60 minutes from the moment the patient arrives to the clinic to perform the test

Inclusion Criteria: patients aged between 18 and 65 years Vagus nerve stimulation implanted for at least 6 months No impedance issues with the VNS electrode Exclusion Criteria: presence of a concomitant laryngeal pathology or RLN damage, independent from vagus nerve stimulation important side effects of the VNS reported by the patient such as dyspnea, pain in neck/ear region and gastrointestinal complaints.