title: Quantitative estimation of the recurrent laryngeal nerve irritation by employing spontaneous intraoperative electromyographic monitoring during anterior cervical discectomy and fusion.
abstract: METHODS
  Prospective, clinical study.
  
  
  OBJECTIVE
  The objective of our study was to evaluate the role of laryngeal intraoperative electromyography (IEMG) in predicting the development of postoperative recurrent laryngeal nerve (RLN) palsy in patients undergoing anterior cervical discectomy and fusion (ACDF). We also attempted to develop a method to quantify the total IEMG irritation of the RLN.
  
  
  BACKGROUND
  RLN injury has been recognized as the most common ACDF-associated neurologic injury. It has been postulated, that the employment of laryngeal IEMG may identify the operative events leading to RLN injury and subsequent postoperative palsy.
  
  
  METHODS
  Laryngeal IEMG monitoring was performed in 298 patients undergoing ACDF. Preexistent baseline EMG activity, amplitude, and duration of IEMG activity were recorded. The total amount of RLN irritation was expressed as an Irritation Score (IS) applying a specially designed mathematical equation incorporating the amplitude, the duration, and the presence of any baseline EMG irritation. The relationship of IEMG activity with parameters such as the number of operative levels, the duration of the procedure, the presence of any previous neck surgeries, and the type of the used retractor was examined.
  
  
  RESULTS
  IEMG activity was recorded in 14.4% of our patients. Postoperative RLN injury occurred in 2.3% of our patients. The sensitivity of IEMG was 100%, the specificity 87%, the positive predictive value 16%, and its negative predictive value 97%. The calculated IS ranged between 0.28 and 3.47 (mean IS: 2.09). Significantly increased IEMG activity was found in patients with previous surgical intervention, patients undergoing multilevel procedures, long-lasting procedures, and cases in which self-retained retractors were used. Likewise, significantly increased IS were observed in patients with previous surgeries and in cases where self-retained retractors were used.
  
  
  CONCLUSIONS
  Our study indicates that laryngeal IEMG is a high-sensitivity modality that can provide real-time information and can potentially minimize the risk of operative RLN injury.
authors.affiliation: Department of Neurosurgery, Medical Center of Central Georgia, School of Medicine, Mercer University, Macon, GA, USA.
authors.forename: Vasilios G
authors.initials: VG
authors.lastname: Dimopoulos
authors.forename: Induk
authors.initials: I
authors.lastname: Chung
authors.forename: Gregory P
authors.initials: GP
authors.lastname: Lee
authors.forename: Kim W
authors.initials: KW
authors.lastname: Johnston
authors.forename: Ioannis Z
authors.initials: IZ
authors.lastname: Kapsalakis
authors.forename: Hugh F
authors.initials: HF
authors.lastname: Smisson
authors.forename: Arthur A
authors.initials: AA
authors.lastname: Grigorian
authors.forename: Joe S
authors.initials: JS
authors.lastname: Robinson
authors.forename: Kostas N
authors.initials: KN
authors.lastname: Fountas
mesh_terms: D002574:Cervical Vertebrae / Q000601:surgery*; D003389:Cranial Nerve Diseases / Q000453:epidemiology / Q000209:etiology / Q000503:physiopathology*; D017586:Diskectomy / Q000009:adverse effects; D004576:Electromyography / Q000379:methods; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D016343:Monitoring, Intraoperative / Q000379:methods*; D011183:Postoperative Complications / Q000209:etiology / Q000503:physiopathology / Q000517:prevention & control; D011446:Prospective Studies; D012009:Recurrent Laryngeal Nerve / Q000503:physiopathology*; D013123:Spinal Fusion / Q000009:adverse effects; D013223:Statistics as Topic / Q000379:methods