title: The Non-Recurrent Laryngeal Nerve: a meta-analysis and clinical considerations.
abstract: BACKGROUND
  The Non-Recurrent Laryngeal Nerve (NRLN) is a rare embryologically-derived variant of the Recurrent Laryngeal Nerve (RLN). The presence of an NRLN significantly increases the risk of iatrogenic injury and operative complications. Our aim was to provide a comprehensive meta-analysis of the overall prevalence of the NRLN, its origin, and its association with an aberrant subclavian artery.
  
  
  METHODS
  Through March 2016, a database search was performed of PubMed, CNKI, ScienceDirect, EMBASE, BIOSIS, SciELO, and Web of Science. The references in the included articles were also extensively searched. At least two reviewers judged eligibility and assessed and extracted articles. MetaXL was used for analysis, with all pooled prevalence rates calculated using a random effects model. Heterogeneity among the included studies was assessed using the Chi2test and the I2statistic.
  
  
  RESULTS
  Fifty-three studies (33,571 right RLNs) reported data on the prevalence of a right NRLN. The pooled prevalence estimate was 0.7% (95% CI [0.6-0.9]). The NRLN was found to originate from the vagus nerve at or above the laryngotracheal junction in 58.3% and below it in 41.7%. A right NRLN was associated with an aberrant subclavian artery in 86.7% of cases.
  
  
  CONCLUSIONS
  The NRLN is a rare yet very clinically relevant structure for surgeons and is associated with increased risk of iatrogenic injury, most often leading to temporary or permanent vocal cord paralysis. A thorough understanding of the prevalence, origin, and associated pathologies is vital for preventing injuries and complications.
authors.affiliation: Department of Anatomy, Jagiellonian University Medical College, Kraków, Poland; International Evidence-Based Anatomy Working Group, Kraków, Poland.
authors.forename: Brandon Michael
authors.initials: BM
authors.lastname: Henry
authors.affiliation: Department of Surgical Sciences, University of Cagliari , Monserrato , Sardinia , Italy.
authors.forename: Silvia
authors.initials: S
authors.lastname: Sanna
authors.affiliation: Department of Anatomy, Jagiellonian University Medical College, Kraków, Poland; International Evidence-Based Anatomy Working Group, Kraków, Poland.
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Graves
authors.affiliation: International Evidence-Based Anatomy Working Group, Kraków, Poland; Division of Medicine, Stavanger University Hospital, Stavanger, Norway.
authors.forename: Jens
authors.initials: J
authors.lastname: Vikse
authors.affiliation: Faculty of Medicine and Surgery, University of Cagliari , Monserrato , Sardinia , Italy.
authors.forename: Beatrice
authors.initials: B
authors.lastname: Sanna
authors.affiliation: Department of Medical Education, Jagiellonian University Medical College , Kraków , Poland.
authors.forename: Iwona M
authors.initials: IM
authors.lastname: Tomaszewska
authors.affiliation: Seattle Science Foundation , Seattle , WA , United States.
authors.forename: R Shane
authors.initials: RS
authors.lastname: Tubbs
authors.affiliation: Department of Anatomy, Jagiellonian University Medical College, Kraków, Poland; International Evidence-Based Anatomy Working Group, Kraków, Poland.
authors.forename: Jerzy A
authors.initials: JA
authors.lastname: Walocha
authors.affiliation: Department of Anatomy, Jagiellonian University Medical College, Kraków, Poland; International Evidence-Based Anatomy Working Group, Kraków, Poland.
authors.forename: Krzysztof A
authors.initials: KA
authors.lastname: Tomaszewski
keywords: Anatomy; Arteria lusoria; Meta-analysis; Non-Recurrent Laryngeal Nerve; Recurrent Laryngeal Nerve