Anatomical variations of recurrent laryngeal nerve: a systematic review and meta-analyses

The aim of this systematic review and meta-analysis was to systematically review and perform a meta-analysis on the anatomical variations of the RLN.

We performed online research for studies that addressed anatomical variations of the RLN and laterality, published between 2015 and 2021. We found 230 articles, and nine were included.

Eight variations were found, with Type I prevailing (41.17%; 95% CI 19.44–64.88), extra laryngeal divergence of the RLN. The other types were: II—fan shape; III—distance greater than 5 mm to the cricothyroid joint; IV—thickening and adipopexy in the elderly; V—non-recurrent laryngeal nerve; VI—intracranial branch; VII—tortuous ascending RLN; and VIII—combination between the inferior branch of the NV and the ascending trunk of the RLN. Types I (p = 0) and III (p < 0.01) prevailed on the left and types II (p < 0.01) and V (p < 0.01) on the right.

It was observed that variations occurred due to the path of the RLN to the entrance to the larynx, its shape, and the age of the evaluated individual. The most frequent variation and side were, respectively, Type I, extra laryngeal divergence and left.