Intraoperative Monitoring for Vagus Nerve Stimulation

Vagus nerve stimulation is a palliative treatment for patients with refractory epilepsy; however, the misplacement of electrodes may cause complications and thus needs to be avoided.

We herein report an intraoperative monitoring technique to prevent the misplacement of electrodes. Endotracheal tube electrodes were inserted to record electromyographic activity from the vocal cords and identify the vagus nerve. Electromyography electrodes were placed on the sternomastoid muscle, sternohyoid muscle, geniohyoid muscle, and trapezius muscle to record muscle activities innervated by the ansa cervicalis. The vagus nerve and ansa cervicalis were electrically stimulated during surgery, and electromyography of the vocal cords and muscles innervated by the ansa cervicalis was recorded. The threshold of vagus nerve activation ranged between 0.05 and 0.75 mA.

The vagus nerve was successfully identified and differentiated from the nerve root of the ansa cervicalis using this technique.

Intraoperative monitoring of the vagus nerve and ansa cervicalis is useful for safe and effective vagus nerve stimulation.