Extralaryngeal branching of the recurrent laryngeal nerve: a meta-analysis of 28,387 nerves

Abstract

Introduction The recurrent laryngeal nerves (RLN) are branches of the vagus nerve that go on to innervate most of the intrinsic muscles of the larynx. Historically, the RLN has been considered to branch after it enters the larynx, but numerous studies have demonstrated that it often branches before. The wide variability of this extralaryngeal branching (ELB) has significant implications for the risk of iatrogenic injury. We aimed to assess the anatomical characteristics of ELB comprehensively. Methods Articles on the ELB of the RLN were identified by a comprehensive database search. Relevant data were extracted and pooled into a meta-analysis of the prevalence of branching, branching pattern, distance of ELB point from the larynx, and presence of positive motor signals in anterior and posterior ELB branches.Results A total of 69 articles (n = 28,387 nerves) from both intraoperative and cadaveric modalities were included in the meta-analysis. The overall pooled prevalence of ELB was 60.0 % (95 % CI 52.0-67.7). Cadaveric and intraoperative subgroups differed with prevalence rates of 73.3 % (95 % CI 61.0-84.0) and 39.2 % (95 % CI 29.0-49.9), respectively. Cadavers most often presented with a ELB pattern of bifurcation, with a prevalence of 61.1 %, followed by no branching at 23.4 %. Branching of the RLN occurred most often at a distance of 1-2 cm (74.8 % of cases) prior to entering the larynx. A positive motor signal was most often noted in anterior RLN branches (99.9 %) but only in 1.5 % of posterior branches. Conclusions The anatomy of the RLN is highly variable, and ELB is likely to have been underreported in intraoperative studies. Because of its high likelihood, the possibility of ELB needs to be assessed in patients to prevent iatrogenic injury and long-term postoperative complications.

Relationship of the recurrent laryngeal nerve to the inferior thyroid artery: A comparison of findings from two systematic reviews

“…From Italy the only other study included in both SRs reported 31.1% (of 280 RLNs) as anterior to ITA (Sturniolo et al, 1999); two additional studies in SR2 involved only 94 and 12 total RLNs. Unweighted results for a specific RLN feature can vary greatly among studies from a single country (as shown by tabulations in Henry et al, 2016bHenry et al, , 2017.…”

“…This study, however, actually did not meet SR1's criterion of having three categories. The 403 RLNs were classified only as either "superficial" (159) or "deep" (244) to ITA at their "first crossing;" 78 referred to "divided" RLNs among the 403 (Page et al, 2003) (i.e., extralaryngeal branching) (Henry et al, 2016b). The terms "superficial" and "deep" have been used elsewhere but not as the only categories for RLN-ITA relationships (Reed, 1943;Bergman et al, 2015).…”

A review of methods for the preservation of laryngeal nerves during thyroidectomy

“…Son yapılan ve 28 327 RLS'yi içeren metaanalizde intraoperatif çalışmalarda ortalama %39.2, kadavra çalışmalarında ise ortalama %73.3 oranında dallanma olduğu belirlenmiştir. [7] Ekstralaringeal dallanma aynı olguda tek taraflı ya da iki taraflı olabilir. [8,9] Zuckerkandl Tüberkülü (ZT): Ultimabrankial cisim (lateral tiroit cismi) ile median tiroit cisminin kaynaşma noktası olduğu kabul edilir ve genellikle posteriora doğru büyüyerek belirgin hale gelebilir.…”

Adaptive self‐organization in the embryo: its importance to adult anatomy and to tissue engineering

“…), innervation of the same structure can differ between individuals (Matejcík, ; Henry et al. ; Wolf et al. ), the number of bones in the cranium can vary due to occasional appearance of wormian (intra‐sutural) bones (Hess, ; Ghosh et al.…”

“…One of the first things that medical students learn of human anatomy, usually to their frustration, is that its details are surprisingly variable. Blood vessels can vary in route and number (D aescu et al 2012;Bertrand et al 2014;Silva et al 2014;Marco-Clement et al 2016;Tomaszewski et al 2017), innervation of the same structure can differ between individuals (Matejc ık, 2010; Henry et al 2016;Wolf et al 2016), the number of bones in the cranium can vary due to occasional appearance of wormian (intrasutural) bones (Hess, 1946;Ghosh et al 2017), and there are many more examples of unpredictable anatomy in anatomical and surgical literature. Some of these differences may be specified genetically, but studies of monozygotic twins have demonstrated that histogenesis can vary even when driven by exactly the same 'genetic programme'.…”