Hua, Xiaoyang1; Diggelmann, Henry 1,2; Jalukar, Vishram1,2; Pagedar, Nitin1
1 Department of Otolaryngology-Head and Neck Surgery, University of Iowa Hospitals and Clinics
2 Department of Otolaryngology-Head and Neck Surgery, Mercy North Iowa Medical Center
Background: A left non-recurrent laryngeal nerve (LNRLN) is an extremely rare anatomic variant. To date, only 4 confirmed cases have been published in English literature. Preoperative prediction of this variant is difficult.
Methods: A 34 year-old female was indicated for thyroidectomy due to a thyroid nodule (2.4X1.6cm) with an FNA showing follicular neoplasm. Preoperative CT scan showed a right sided aorta (RSA), an aberrant left subclavian artery (ALSA), and absence of a Kommerell diverticulum (KD) (Figure 1-4). We then predicted a LNRLN.
Results: a LNRLN was confirmed during thyroidectomy. It came off directly from the vagus nerve and entered the larynx behind the cricothyroid joint (Figure 5).
Discussion and conclusion: The inferior laryngeal nerve is associated with the 6th aortic arch. The development of a LNRLN requires the regression of both the 4th (aortic arch) and the 6th (ductus arteriosus, DA) arches on the left side. A RSA with an ALSA results from the persistence of the right 4th arch and partial regression of the left 4th arch. Thus, the development of a LNRLN in patients with RSA and ALSA requires the absence of DA on the left side. Radiologic determination of DA is difficult when it is closed. The absence of a Kommerell diverticulum at the take-off of ALSA from the RSA in these patients may be due to the lack of high pressure blood flow from the pulmonary artery to the ALSA during fetal development. It may radiologically predict the absence of DA and presence of a LNRLN in these patients.
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