title: Intraoperative monitoring: normative range associated with normal postoperative glottic function.
abstract: OBJECTIVE
  Despite increasing use of intraoperative nerve monitoring (IONM), there is limited information on normative electrophysiologic electromyographic (EMG) parameters. The objective of this study was to define normative parameters of recurrent laryngeal nerve (RLN) intraoperative neuromonitoring during thyroid surgery associated with normal postoperative vocal cord function.
  
  
  METHODS
  Prospective data collection in a tertiary care center.
  
  
  METHODS
  Quantitative analysis of evoked waveform amplitude and threshold was performed on 125 patients with 167 nerves at risk. Values were displayed as a mean with 5th percentile and 95th percentiles (5th-95th). Postoperative vocal cord function in all patients was documented.
  
  
  RESULTS
  All patients had normal postoperative laryngeal function (group I-normal) except for two patients who had postoperative transient vocal cord paralysis (group II-abnormal/outlier). The final amplitude between 247 and 3607 μV at the end of dissection/end of surgery was associated in all group I patients with a normal postoperative neural function. Final intraoperative amplitude measures for group II averaged just 97.5 μV, significantly different than our normative ranges obtained for group I, and fell outside of the group I 5% to 95% percentile range (P = .016). Final amplitude adequately predicted postoperative RLN impaired function immediately after surgery.
  
  
  CONCLUSIONS
  We propose IONM EMG data criteria that predict normal postoperative vocal cord function monitoring and provide information about nerve functioning at the end of the operation, thereby allowing adaptation of the surgical strategy when a bilateral procedure is indicated to avoid bilateral nerve paralysis.
authors.affiliation: Division of Thyroid and Parathyroid Surgery, Massachusetts Eye and Ear Infirmary, Boston.
authors.forename: Diana
authors.initials: D
authors.lastname: Caragacianu
authors.forename: Dipti
authors.initials: D
authors.lastname: Kamani
authors.forename: Gregory W
authors.initials: GW
authors.lastname: Randolph
mesh_terms: D004576:Electromyography; D005500:Follow-Up Studies; D005931:Glottis / Q000294:innervation / Q000502:physiology*; D006801:Humans; D007828:Laryngoscopy; D016343:Monitoring, Intraoperative / Q000379:methods*; D011183:Postoperative Complications; D011184:Postoperative Period; D011379:Prognosis; D011446:Prospective Studies; D020127:Recovery of Function; D012009:Recurrent Laryngeal Nerve / Q000502:physiology*; D013965:Thyroidectomy / Q000009:adverse effects*; D014826:Vocal Cord Paralysis / Q000175:diagnosis* / Q000209:etiology; D014827:Vocal Cords / Q000502:physiology
keywords: Intraoperative nerve monitoring; bilateral vocal cord palsy; complications of thyroid surgery; normal parameters; postoperative glottis and/or recurrent laryngeal nerve function; recurrent laryngeal nerve