Successful Prediction of a Left Nonrecurrent Laryngeal Nerve in a Patient With Right-Sided Aorta and Aberrant Left Subclavian Artery.

BACKGROUND: Left nonrecurrent laryngeal nerve (LNRLN) is an extremely rare anatomic variant. The development of such anatomic variation requires the regression of both the fourth (aortic arch) and sixth (ductus arteriosus, DA) arches on the left side. Preoperative prediction of this variant is difficult but might reduce risk of nerve injury. METHODS: A 34-year-old female was indicated for thyroidectomy for a 2.4 cm follicular neoplasm and Graves' disease. Due to a positive medical history of 22q11.2 microdeletion and unexplained left vocal cord paralysis, a preoperative chest computed tomography (CT) scan was obtained and revealed a right-sided aorta (RSA) and aberrant left subclavian artery (ALSA) without Kommerell's diverticulum. A left-sided NRLN was then highly suspected. RESULTS: Thyroidectomy was performed under general anesthesia with the utilization of intraoperative laryngeal nerve monitoring. A LNRLN was confirmed intraoperatively. CONCLUSIONS: Right-sided aorta and ALSA indicate embryologic regression of the left fourth primitive aortic arch. The absence of Kommerell's diverticulum at the origin of the ALSA indicates the lack of high-pressure blood flow from the pulmonary artery to the ALSA through the ductus arteriosus during embryogenesis, suggesting the embryologic regression of the left sixth primitive aortic arch. The presence of all 3 radiologic features thus highly suggests the possibility of a LNRLN.