title: The nonrecurrent laryngeal nerve: A clinical anatomic mapping with regard to intraoperative neuromonitoring.
abstract: We investigated the nonrecurrent inferior laryngeal nerve (nrILN), an important variant in the course of the inferior laryngeal nerve (ILN; 0.5-6.0%). Its importance was demonstrated in a clinical case as well as in cadaver specimens, and the pattern was identified with intraoperative neuromonitoring (IONM).
  
  
  
  The ILN and the presence of an nrILN were investigated in 36 formaldehyde-embalmed specimens. Our anatomic findings showed differences in the anatomic course of the ILN and thus produced possible explanations for different IONM signals that would correlate with differences in the anatomic course of the ILN. Preoperative ultrasonographic evaluation of the brachiocephalic trunk and the recurrent laryngeal nerve were used for the exclusion or identification of an nrILN, respectively.
  
  
  
  We found 2 nrILNs (ascending, horizontal; 6%) in the anatomic specimens. These 2 specimens each showed an aberrant right subclavian artery (lusorial artery) and were, therefore, associated with the absence of a brachiocephalic trunk. The intraoperative case displayed a descending nrILN. Signals derived from the vagus nerve were positive if derived proximal to and negative if derived distal to the branching of an nrILN. By ultrasonographic identification of a normal brachiocephalic trunk, an nrILN could be excluded.
  
  
  
  Surgeons need a working knowledge about nrILNs to avoid recurrent nerve palsy and should be familiar with all the possible course variations in the ILN when IONM signals are absent with vagal stimulation. Moreover, endocrine surgeons need to be able to interpret correctly negative as well as positive signals. Preoperative ultrasonography should ideally be performed, because the presence of a normal brachiocephalic trunk is a quick method to exclude or identify a nrILN.
authors.affiliation: Division of Clinical and Functional Anatomy, Department of Anatomy, Histology and Embryology, Medical University of Innsbruck, Innsbruck, Austria. Electronic address: marko.konschake@i-med.ac.at.
authors.forename: Marko
authors.initials: M
authors.lastname: Konschake
authors.affiliation: Division of Clinical and Functional Anatomy, Department of Anatomy, Histology and Embryology, Medical University of Innsbruck, Innsbruck, Austria.
authors.forename: Marit E
authors.initials: ME
authors.lastname: Zwierzina
authors.affiliation: Division of Clinical and Functional Anatomy, Department of Anatomy, Histology and Embryology, Medical University of Innsbruck, Innsbruck, Austria.
authors.forename: Elisabeth J
authors.initials: EJ
authors.lastname: Pechriggl
authors.affiliation: Division of Clinical and Functional Anatomy, Department of Anatomy, Histology and Embryology, Medical University of Innsbruck, Innsbruck, Austria.
authors.forename: Bernhard
authors.initials: B
authors.lastname: Moriggl
authors.affiliation: Division of Clinical and Functional Anatomy, Department of Anatomy, Histology and Embryology, Medical University of Innsbruck, Innsbruck, Austria.
authors.forename: Erich
authors.initials: E
authors.lastname: Brenner
authors.affiliation: Division of Clinical and Functional Anatomy, Department of Anatomy, Histology and Embryology, Medical University of Innsbruck, Innsbruck, Austria.
authors.forename: Romed
authors.initials: R
authors.lastname: Hörmann
authors.affiliation: General and Endocrine Surgery, Sanatorium Kettenbrücke GmbH, Innsbruck, Austria.
authors.forename: Rupert
authors.initials: R
authors.lastname: Prommegger
mesh_terms: D002102:Cadaver; D004210:Dissection; D004558:Electric Stimulation; D006801:Humans; D007823:Laryngeal Nerves / Q000473:pathology* / Q000503:physiopathology*; D008297:Male; D016343:Monitoring, Intraoperative; D013959:Thyroid Diseases / Q000601:surgery*; D013965:Thyroidectomy