The Anatomical Variation of Recurrent Laryngeal Nerve in Relation to Inferior Thyroid Artery in Thyroid Surgeries

Abstract Background: This study was conducted to assess the Anatomical Variation of Recurrent Laryngeal Nerve in Relation to Inferior Thyroid Artery in thyroid surgeries. Material and methods: Patient records from thyroidectomy (with or without parathyroidectomy) procedures utilizing intraoperative neural monitoring (IONM) were retrospectively analyzed. The study focused on identifying anatomical variations of the recurrent laryngeal nerve (RLN) and its association with the inferior thyroid artery (ITA), as well as exploring their connection to vocal cord paralysis (VCP). There were total 90 subjects who had been divided into three groups of 30 each on the basis of type of the nerve involved. Group 1 comprised of subjects in which anterior RLN was involved. Group 2 comprised of subjects in which posterior RLN was involved and Group 3 comprised of subjects in which LN between the branches of ITA was involved. All the results were evaluated. Results: Among the subjects in which anterior RLN was involved, branching was seen in 16 subjects and non-branching was observed in 14 subjects. Among the subjects in which posterior RLN was involved, branching was seen in 11 subjects and non-branching was observed in 18 subjects. Among the subjects in which RLN between the branches of ITA was involved, branching was seen in 10 subjects and non-branching was observed in 20 subjects. The overall incidence of vocal cord paralysis (VCP) observed in the study was 5.2%, with temporary VCP accounting for 4.9% and permanent VCP for 0.3% (see Table 5). When comparing nerve branching patterns, both the total VCP rate and the rate of temporary VCP were significantly elevated in cases involving branching recurrent laryngeal nerves (RLNs) compared to non-branching ones. The total VCP rates also varied based on the anatomical relationship between the RLN and the inferior thyroid artery (ITA): 8.6% when the RLN passed anterior to the ITA, 3.4% when it was posterior, and 1.7% when it traversed between ITA branches, with these differences reaching statistical significance. Conclusion: Anterior crossing of the recurrent laryngeal nerve (RLN) over the inferior thyroid artery (ITA) and the presence of RLN branching are common anatomical variations that elevate the risk of vocal cord paralysis (VCP) during thyroidectomy. These variations are typically undetectable before surgery.