This prospective series of total thyroidectomies revealed that the position of RLN relative to ITA was consistent with the posterior RLN-ITA pattern in most of patients, regardless of the side of RLN, followed by the anterior and the between patterns.

In a meta-analysis of 79 studies (14,269 nerves) on the relationship of the RLN to the ITA, the left versus right-sided comparison revealed that RLNs were predominantly posterior (62.6% vs 37.0%) on the left side and anterior (17.2% vs 37.1%) on the right side [3].

In a systematic review of 16 studies (12 cadaveric, 4 intraoperative) including 4198 RLNs in 2099 patients, the most common type of RLN was concluded to be the posterior to the ITA (52.08%), followed by anterior to the ITA (23.91%) and between the branches of the ITA (18.94%), along with higher likelihood of posterior type in the RLNs on the left side vs. those on the right side (35.73% vs. 20.78%) [4]. Hence, RLN is considered to run anterior to the ITA on the right side and posterior to the ITA on the left side, while it rarely passes between the branches of the ITA [3, 4].

Notably, our findings seem to differ in this respect given that a higher prevalence of posterior RLN-ITA pattern was noted overall, in addition to the likelihood of RLN also to lay predominantly posterior to ITA on the right side. Likewise, in a previous study from Turkey in 253 patients with thyroidectomy, the RLN was found to lay posterior to ITA, anterior to ITA and in between branches of ITA in 64.1%, 24.1%, and 8% of dissected nerves on the right side and in 71.5%, 19.7%, and 5.4% of dissected nerves on the left side, respectively [6]. The authors also noted no significant difference between left and right sides concerning the relation of the RLN to the ITA with high rates of posterior RLN-ITA pattern on both the left (64.1%) and the right (71.5%) sides, consistent with our findings (74.1% and 68.4%, respectively) [6].

Although our findings indicate a safer position of RLN on the right side in terms of lower likelihood of showing patterns (anterior, between) with a high risk of injury, it should be noted that the anatomical relationship between RLN and ITA is primarily volatile which shows asymmetry with differences even on either side in the same patient in more than 60% of cases [1,2,3,4, 7,8,9,10,11].

In a recent analysis of thyroidectomy-specific database involving 11,370 patients, RLN injury after thyroidectomy occurred in 6.0% of patients overall, and more often in malign vs. benign indications (9.0% vs. 4.3%), in thyroidectomies vs. lobectomies (6.9% vs. 4.3%), while multivariate analysis also revealed that RLN injury was independently associated with total thyroidectomy (OR 1.4) and diagnosis of thyroid malignancy (OR 2.1) [12]. In our series, all patients had total thyroidectomy which was performed due to diagnosis of malignancy in majority of cases, emphasizing the likelihood of our patients to be at increased risk of RLN injury and thus the critical role of intraoperative RLN identification through reliable anatomical landmarks in minimizing the risk of injury.

Hence, given that relationship between the RLN and the ITA is quite variable with a significant incidence of RLN/ITA variation on both sides, our findings suggest that ITA should not be used as the sole landmark for RLN dissection due to its unpredictability, and other viable landmarks should also be considered while planning, exposing, and performing operations in the neck to minimize the risk of iatrogenic injury to patients [1, 3, 4, 6, 8, 13].