Nonrecurrent Laryngeal Nerve: Precise Detection by Electrophysiological Nerve Monitoring

Abstract

Complication-free thyroid surgery is mainly based on the motor integrity of the recurrent laryngeal nerve (RLN). The nonrecurrent laryngeal nerve (non-RLN) is a rare anatomical variation that may increase the risk of vocal cord palsy. Early identification and exposure of the non-RLN may minimize injury risk. This case report presents functional detection of the non-RLN by intraoperative neuromonitoring (IONM).Total thyroidectomy was performed under the guidance of IONM on a patient with bulky multinodular goiter. The first step of IONM is pre-dissection stimulation (V1) of the right vagus nerve (VN). V1 at a standard distal point was negative as indicated by the absence of both a sound signal and wave amplitude. The right VN was then followed proximally and dissected under the guidance of IONM. This dissection established a proximal point creating a positive signal that led us to determine the separation point of the non-RLN. The right non-RLN arising from the proximal VN was identified and fully exposed until laryngeal entry. Its motor integrity was confirmed with post-dissection signals. The left RLN was identified at the usual anatomical position that was fully exposed and preserved during thyroid surgery. Total thyroidectomy was then accomplished without complication. The postoperative period was uneventful. Postoperative laryngoscopy confirmed normal vocal cord function.The non-RLN is accurately identified by IONM during the early part of the thyroid surgery. The absence of a distal VN signal is predictive of the non-RLN. IONM-guided proximal dissection of the right VN leads to the identification of the non-RLN. The prediction of the non-RLN by the absence of a VN signal during an early stage of surgery may prevent or minimize the risk of nerve injury.

Systematic Review and Meta-Analysis: Recurrent Laryngeal Nerve Variants and Their Implication in Surgery and Neck Pathologies, Using the Anatomical Quality Assurance (AQUA) Checklist

“…To avoid bias, we excluded all studies that had an N equal to one [ 61 ] and studies reporting a prevalence of 100% [ 54 , 62 , 63 ] because the sample was chosen intentionally or for convenience and therefore gave this result. Fifteen studies met the criteria to be meta-analyzed based on the prevalence variable.…”

“… Forest plot of prevalence of RLN variations of the included studies [ 3 , 7 , 12 , 15 , 29 , 32 , 33 , 35 , 38 , 39 , 40 , 41 , 42 , 61 , 63 ]. …”

The triad of non-recurrent laryngeal nerve; three associated predicting variants in the era of nerve monitoring: A case report

“…The non-RLN was precisely predicted and successfully detected at the early intraoperative period by IONM with a negative distal V1 signal. Early successful identification of the non-RLN by the routine application of IONM allows the cautious preservation of the nerve and avoidance of injury to the nerve [ [1] , [2] , [3] , [4] , 6 , 12 , 18 ]. In thyroid surgery, before IONM, the non-RLN could be identified by coincidence during visual dissection.…”

Left Non-Recurrent Laryngeal Nerve without any anatomical malformation. Can the use of neuromonitoring help to its identification?

“…El hallazgo sorprendente de esta paciente es la ausencia de variaciones anatómicas cardiovasculares demostradas en la angio tomografía de tórax, lo cual es el patrón en los casos reportados. Aunque están descritos en ingles pocos casos sobre esta rara presentación del nervio no recurrente izquierdo, no encontramos artículos similares en español (7,8) .…”