Nerve Stimulation Monitoring

Andrew Biello, MD

Content Contributor

Evolution of Nerve Stimulation Monitoring

Nerve stimulation during thyroidectomy has been described in the 1940s, where palpation of the larynx during recurrent laryngeal nerve stimulation was used as a confirmatory measure. In the 1980’s, palpation of the posterior cricoarytenoid muscle, with concurrent nerve stimulation, was described as an intraoperative measure.

These measures are grouped into the category of intermittent intraoperative nerve monitoring. In the early 2000’s, continuous intraoperative nerve monitoring gained popularity as a means to monitor nerve function throughout an entire surgery. Continuous monitoring while in close proximity to nerves can help achieve complete resection, while keeping a safe distance from nerve structures.

Technology Spotlight

Medtronic NIM-Response 3.0 Nerve Monitor

The Medtronic NIM monitor is an example of a continuous intraoperative nerve monitor, with applications in a number of Head and Neck Cancer surgeries. For thyroidectomy, the NIM EMG endotracheal tube provides both an airway for intraoperative ventilation, as well as nerve monitoring for the vagus or recurrent laryngeal nerves. It does so by detecting movement of the muscles of the larynx.

Cross bands on the tube guide its placement during intubation, and should be placed at the level of the vocal cords. After identification of the recurrent laryngeal nerve, confirmation can be achieved via stimulation with the NIM probe, and evaluation of vocalis muscle activity response on the monitor.

The continuous monitoring system will also notify the surgeon of a change in nerve status in the event of an accidental transection, at which time re-anastomosis can be attempted. Immediate identification of nerve injury can potentially save the patient from another dedicated surgery for nerve repair.