A systematic review of variations of the recurrent laryngeal nerve.

With thyroid cancer fast becoming one of the most common endocrine cancers, the frequency of thyroid surgery has increased. A common and debilitating concern with thyroid surgery is recurrent laryngeal nerve (RLN) paralysis leading to glottal obstruction and airway compromise. A systematic review regarding the anatomical variation of the recurrent laryngeal nerve was performed to determine the position of anatomical variants of the RLN in relation to the inferior thyroid artery (ITA) as well as the prevalence of nonrecurrent laryngeal nerve (NRLN). MEDLINE, Web of Science, MEDITEXT, AMED, CINAHL, Cochrane, ProQuest, Pubmed, and ScienceDirect. Databases were searched using the search terms "inferior thyroid artery," "recurrent laryngeal nerve," "nonrecurrent laryngeal nerve," and "anatomical variation." The reference sections of the articles found were searched for additional reports. The references of all articles were searched to find articles missed in the database search. A total of 8,655 RLN sides were included in this study. One thousand eight hundred and thirteen (20.95%; 95% confidence interval (CI) 20.09, 2,182) showed a Type A configuration of RLN in relation to the ITA, 2,432 (28.10%; 95% CI 27.15, 29.06) showed a Type B configuration and 4,410 (50.95%; 95% CI 49.89, 52.01) showed a Type C configuration between the RLN and the ITA. The second search returned with 38,568 recurrent laryngeal sides and only 221 (0.57%; 95%CI 0.5, 0.65) NRLN documented. The RLN is most commonly found in the posterior position, relative to the ITA. The incidence of the NRLN is low, only occurring in 0.57% of people.