S209 – Optimal Electrode Position for ENoG for Facial Palsy

Objectives To develop a more simple procedure for electroneurography (ENoG) of facial palsy for assessing prognosis, we conducted a preliminary study to examine an optimal electrode position for recording evoked compound muscle action potentials (CMAPs) of the perioral muscles. Methods We evaluated a new method called the submentall method, in which the electrode connected to the negative input (G1) was placed on the skin over the orbicularis oris muscle, and the other electrode connected to the positive input of the amplifier (G2) was placed on the mental protuberance. We compared the amplitudes and morphology between the CMAPs recorded with this method and those recorded using the standard electrode positions (G1 placed on the skin over the orbicularis oris muscle; G2 placed on the nasolabial fold, closely lateral to the ala nasi). Furthermore, the amplitudes and waveforms of CMAPs were recorded from 4 different G1 positions on the skin over the orbicularis oris muscle, with G2 set on the mental protuberance. The main trunk of the facial nerve was stimulated by percutaneous supramaximal electrical stimulation beneath the auricle. Results The submental method gave greater amplitudes and more obvious biphasic CMAPs than those produced with the standard method. In the submental method, the optimal G1 recording electrode position was on the philtrum. Conclusions This recording procedure has the potential to be a simpler and more reliable method for calculating ENoG values than the standard method. However, further studies to establish prognostic criteria of ENoG for facial palsy are needed.