title: The weepy nerve-different sensitivity of left and right recurrent laryngeal nerves under tensile stress in a porcine model.
abstract: OBJECTIVE
  Recurrent laryngeal nerve palsy in thyroid surgery is still a threatening complication. Our aim was to analyze the impact of prolonged tensile stress on the recurrent laryngeal nerve (RLN) in an animal model using continuous intraoperative neuromonitoring (C-IONM).
  
  
  METHODS
  Constant tensile stress was applied to left and right RLNs in 20 pigs (40 RLN). In a pilot study, five animals were subjected to a tensile force of 0.34 ± 0.07 N for 10 min and changes in amplitude were documented using C-IONM. In the main study, a force of 1.2 N was applied until the signal amplitude was reduced by 85 %, in 15 pigs. Nerve conductivity was analyzed by threshold current measurements.
  
  
  RESULTS
  Good correlation was found between stress and amplitude decrease in the pilot study as well as between signal decrease and duration of trauma in the main study. Great variations were found inter- and intra-individually. These variations were most prominent at 85 % signal reduction (median 36 min, range 0.3-171 min). There was no side specificity (left 0.3-171 min, right 0.3-168 min, respectively, p = 0.19). However, in each individual animal, there was a sensitive (0.3-98.9 min) and less sensitive nerve (26.8-171 min). These differences became highly significant at 85 % of signal reduction (p = 0.008), where the vulnerability is 1.4 to 146.4 times higher on one side (mean 4.3).
  
  
  CONCLUSIONS
  Our study demonstrates the presence of a sensitive RLN that was 4.3 times more vulnerable than the contralateral nerve (range 1.4-146.4 times, p = 0.008). Thus, the right and the left nerves cannot be assumed to be of equal sensitivity to trauma. In our data, the more sensitive nerve does not occur predominantly on one side and was named the "weepy nerve."
authors.affiliation: Allgemein- und Viszeralchirurgie, HELIOS Spital Überlingen, Härlenweg 1, Überlingen, Germany. wolfram@lamade.de.
authors.forename: Wolfram
authors.initials: W
authors.lastname: Lamadé
authors.affiliation: Allgemein- und Viszeralchirurgie, HELIOS Spital Überlingen, Härlenweg 1, Überlingen, Germany.|Klinik für Neurologie, Krankenhaus Nordwest, Frankfurt am Main, Germany.
authors.forename: Maren
authors.initials: M
authors.lastname: Béchu
authors.affiliation: Allgemein- und Viszeralchirurgie, HELIOS Spital Überlingen, Härlenweg 1, Überlingen, Germany.
authors.forename: Ester
authors.initials: E
authors.lastname: Lauzana
authors.affiliation: Friedrich-Loeffler-Institut, Bundesforschungsinstitut für Tiergesundheit, Neustadt, Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: Köhler
authors.affiliation: Friedrich-Loeffler-Institut, Bundesforschungsinstitut für Tiergesundheit, Neustadt, Germany.
authors.forename: Sabine
authors.initials: S
authors.lastname: Klein
authors.affiliation: Allgemein- und Viszeralchirurgie, HELIOS Spital Überlingen, Härlenweg 1, Überlingen, Germany.
authors.forename: Tuncay
authors.initials: T
authors.lastname: Tuncer
authors.affiliation: Allgemein- und Viszeralchirurgie, HELIOS Spital Überlingen, Härlenweg 1, Überlingen, Germany.
authors.forename: Noor Isra Heryantee
authors.initials: NI
authors.lastname: Rashid
authors.affiliation: Friedrich-Loeffler-Institut, Bundesforschungsinstitut für Tiergesundheit, Neustadt, Germany.
authors.forename: Erich
authors.initials: E
authors.lastname: Kahle
authors.affiliation: Airbus Defence and Space, Immenstaad, Germany.
authors.forename: Bertram
authors.initials: B
authors.lastname: Erdmann
authors.affiliation: Klinik für Neurologie, Krankenhaus Nordwest, Frankfurt am Main, Germany.
authors.forename: Uta
authors.initials: U
authors.lastname: Meyding-Lamadé
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D005260:Female; D008297:Male; D016343:Monitoring, Intraoperative; D009431:Neural Conduction / Q000502:physiology*; D012009:Recurrent Laryngeal Nerve / Q000503:physiopathology*; D013314:Stress, Mechanical; D013552:Swine; D013718:Tensile Strength; D014143:Traction; D014826:Vocal Cord Paralysis / Q000209:etiology / Q000503:physiopathology*
keywords: Left and right RLNs; Neuromonitoring; Recurrent laryngeal nerve palsy; Tensile stress