Continuous monitoring of the recurrent laryngeal nerve

The objective of this study was to assess the safety and utility of continuous intraoperative neuromonitoring for the prevention of recurrent laryngeal nerve injury during thyroidectomy.

A prospective cohort study was conducted in consecutive patients undergoing thyroidectomy. Variations in amplitude and distal latency of the electromyogram (EMG) were assessed. In the case of suspicious events, restorative manoeuvers were performed to attempt to recover the potentials. Associations were explored between findings in laryngoscopy 24 h after surgery and intraoperative neurophysiological events.

In the study, 248 consecutive thyroidectomies were included, which were carried out between January 2012 and December 2015. Continuous vagal nerve monitoring was not associated with adverse cardiopulmonary events. Among the 400 at-risk recurrent laryngeal nerves (RLNs), there were eight nerves showing temporary palsy (2%). While an increase in distal latency of > 10% did not provide any relevant information, a decrease in the amplitude of the EMG of > 50% was associated with a higher risk of RLN palsy. A decrease in the amplitude of the EMG of > 50% was associated with negative and positive predictive values of 100 and 47%, respectively. Recovery manoeuvers reversed the decline in the amplitude of potentials in 80% of cases.

Continuous vagal nerve monitoring is safe and allows us to assess nerve function intraoperatively. A decrease of more than 50% in the amplitude of the potentials from EMG baseline is a warning sign of the development of a nerve injury. Nevertheless, this decrease is reversible with restorative manoeuvers, making it possible to minimise RLN injuries.