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

INTRODUCTION AND IMPORTANCE: The prediction and early identification of non-recurrent laryngeal nerve (RLN) may minimize risk of injury. It could be associated with other coincident variants that predict non-RLN, leading to its proper identification. CASE PRESENTATION: A patient with multinodular goiter underwent total thyroidectomy under intraoperative neuromonitoring (IONM) guidance. Preoperative thoracic computerized tomography (CT) scan/angiography revealed aberrant right subclavian artery (ARSA). During thyroid surgery, the vagus nerve (VN) was identified in the neurovascular bundle. An anatomic variation of the VN was observed, as it was medially placed in relation to the common carotid artery (CCA). Pre-dissection electrophysiological stimulus of the VN (V1) was negative. Thus, a right non-RLN was identified with careful surgical dissection. The branching point of the non-RLN on the VN was identified, and non-RLN was fully exposed until the laryngeal entry. IONM revealed that V1 signal was negative if derived distal to the non-RLN separation, and positive if derived proximal to the non-RLN separation. CLINICAL DISCUSSION: ARSA detected by preoperative CT scan is associated with non-RLN. The medial course of the VN in relation to the CCA was found as a coincident anatomic variant with the non-RLN. Absence of pre-dissection V1 signal by IONM was an electrophysiological variant associated with the non-RLN. CONCLUSION: ARSA is a reliable variant for predicting the non-RLN. VN medial to the CCA and absence of electrophysiological V1 signal could precisely predict the non-RLN. Therefore, the coincidence of three anatomical and electrophysiological variants with non-RLN could lead to the prediction of non-RLN.