Modification of the Surgical Strategy for the Dissection of the Recurrent Laryngeal Nerve Using Continuous Intraoperative Nerve Monitoring

Abstract

Background The aim of this study was to describe first experiences and changes in management using continuous intraoperative neuromonitoring (C-IONM) in thyroid and parathyroid surgery. Method Retrospective analysis of patients who underwent surgery with C-IONM since 2012. Surgical maneuvers were modified when electrophysiologic events occurred. Patients with persistent loss of signal (LOS) underwent postoperative laryngoscopy. Results One hundred and one patients (of 1586 neck surgeries) were included and 19 had events: In 13 these were temporary (resolved before end of surgery) and led to intraoperative modifications in surgical approach; in all cases traction was released, and in 8, recurrent laryngeal nerve (RLN) approach was changed [superior approach (2), inferior approach (2), both (4)]. Six patients had persistent LOS (5.9%, present at end of procedure), with RLN palsy (RLNP) on postoperative day 1: In three, LOS occurred at electrode placement on the vagus nerve, leading to distal placement of the electrode allowing ipsilateral dissection under continuous monitoring; all three had complete recovery at 6 months. In the three other patients, LOS occurred on the RLN: one probable thermal, one traction lesion and one accidental section of the anterior RLN branch. The RLN recovered within 6 months in two patients, and in the third, RLNP persisted after 6 months (1/101 = 1%). Conclusion C-IONM provides real-time evaluation of the RLN function, allowing for adaptation of surgical maneuvers to prevent RLNP. It seems particularly useful in difficult cases like redo neck surgery, invasive thyroid cancer and intrathoracic or large goiter. Care should be given at electrode placement on the vagus nerve.

Limits of continuous neural monitoring in thyroid surgery

“…Even though in contrast with our title statement, Chávez et al's report and other recent studies have shown that CIONM is associated with significant less permanent recurrent laryngeal nerve (RLN) injuries compared to intermitted neural monitoring (IONM) [1][2][3][4][5].…”

“…CIONM represents a gradually surgical progress, achieving and advancing to the objective of less RLN injuries [1][2][3][4][5].…”

Noninvasive, tube‐based, continuous vagal nerve monitoring using the laryngeal adductor reflex: Feasibility study of 134 nerves at risk

“…This methodological advantage makes LAR‐C‐IONM attractive for minimally invasive approaches, both endoscopic and open, in addition to alternative surgical approaches to neck endocrine surgery, such as transoral and transaxillary. Additionally, LAR‐C‐IONM is a safe technique that eliminates the need for manipulation of the vagus nerve and avoids the possibility of vagal electrode displacement intraoperatively, which disrupts the core analysis of the Automatic Periodic Stimulation system for detecting significant CMAP decrements …”

“…Additionally, LAR-C-IONM is a safe technique that eliminates the need for manipulation of the vagus nerve and avoids the possibility of vagal electrode displacement intraoperatively, which disrupts the core analysis of the Automatic Periodic Stimulation system for detecting significant CMAP decrements. 10,11,17,18 Although LAR is still an evolving technique, our experience is that it is exquisitely sensitive to changes in efferent neuron excitability induced by RLN stretch or compression. This sensitivity necessitates frequent intraoperative relaxation of retracted tissues in some patients to assess for reversibility of observed LAR-C-IONM amplitude decrements because traction injuries are reversible when prompt corrective measures are applied.…”

“…Until recently, the only method of C-IONM requires placement of a stimulating electrode around the vagus nerve, which can become displaced intraoperatively and requires dissection between the common carotid artery and internal jugular vein. 10,11 In the first half of 2017, we published a case series of 15 patients whose RLNs were continuously monitored during thyroid and cervical spine surgeries using no equipment other than an EMG endotracheal tube. 12 Herein, we present the first large series of patients (100 patients, 134 nerves-at-risk) continuously monitored during neck endocrine procedures using the laryngeal adductor reflex (LAR-C-IONM), in addition to conventional I-IONM.…”