The Laryngoscope C 2014 The American Laryngological, V
Rhinological and Otological Society, Inc.
Stimulation Threshold Greatly Affects the Predictive Value of Intraoperative Nerve Monitoring Daniel L. Faden, MD; Lisa A. Orloff, MD; Tokunbo Ayeni, BS; Daniel S. Fink, MD; Katherine Yung, MD Objectives/Hypothesis: Using a standardized, graded, intraoperative stimulation protocol, we aimed to delineate the effects of various stimulation levels applied to the recurrent laryngeal nerve on the postoperative predictive value of intraoperative nerve monitoring. Study Design: A total of 917 nerves at risk were included for analysis. Intraoperatively, patients underwent stimulation of the recurrent laryngeal nerve at 0.3, 0.5, 0.8, and 1.0 mA followed by postoperative laryngoscopy for correlation with intraoperative findings. Methods: Sensitivity, specificity, positive predictive value, and negative predictive value were calculated at each stimulation level. Results: Sensitivity, specificity, positive predictive value, and negative predicative values ranged from 100% to 37%, 6% to 99%, 2% to 39%, and 100% to 99%, respectively at 0.3 to 1.0 mA. No demographic variables affected sensitivity or specificity. Receiver operating characteristic analysis identified 0.5 mA as the level of stimulation that optimizes sensitivity and specificity. Conclusions: The predictive value of intraoperative nerve monitoring varies greatly depending on the stimulation levels used. At low amplitudes of stimulation, nerve monitoring has high sensitivity and negative predictive value but low specificity and positive predictive value, related to the high rate of false positives. At high levels of stimulation, specificity and negative predictive value are high, sensitivity is low, and the positive predictive value rises as the rate of false negatives increase and the rate of false positives decrease. A stimulation level of 0.5 mA optimizes the predictive value of nerve monitoring; however, stimulation at multiple levels significantly improves the predictive value of intraoperative nerve monitoring. Key Words: Recurrent laryngeal nerve, intraoperative nerve monitoring, thyroid surgery. Level of Evidence: 2b. Laryngoscope, 125:1265–1270, 2015
INTRODUCTION Surgery that puts the recurrent laryngeal nerve (RLN) at risk, including thyroidectomy, parathyroidectomy and central neck dissection, is on the rise in the United States as the population ages and the incidence of thyroid cancer increases.1 Although occurring in only about 3% of patients,2,3 damage to one or both RLNs can result in significant morbidity including voice changes, dysphagia, dyspnea, or airway distress, and need for tracheostomy or other interventions. Previously published
Additional Supporting Information may be found in the online version of this article. From the Department of Otolaryngology–Head and Neck Surgery (D.L.F., K.Y.) and School of Medicine (T.A.), University of California, San Francisco, San Francisco, California; Department of Otolaryngology– Head and Neck Surgery (L.A.O.), Stanford University, Stanford, California; and the Department of Otolaryngology–Head and Neck Surgery (D.S.F.), Louisiana State University Health Sciences Center, New Orleans, Louisiana, U.S.A. Editor’s Note: This Manuscript was accepted for publication September 15, 2014. Presented at the Triological Society 117th Annual Meeting at COSM, Las Vegas, Nevada, U.S.A., May 15–16, 2014. The authors have no funding, financial relationships, or conflicts of interest to disclose. * Send correspondence to Daniel Faden, MD, UCSF Department of Otolaryngology–Head and Neck Surgery, 2380 Sutter Street, First Floor, San Francisco, CA, 94115. E-mail: [email protected] DOI: 10.1002/lary.24960
Laryngoscope 125: May 2015
studies have not shown that use of intraoperative nerve monitoring (IONM) decreases the rate of injury to the RLN2,3; however, use of IONM has become increasingly widespread. In recent surveys, approximately 80% of otolaryngologists and 48% of general surgeons reported using IONM, and 44% of otolaryngologists and 31% of general surgeons use IONM routinely.4,5 More recently, interest has focused on the predictive value of IONM for intraoperative decision making (i.e., decision to proceed with contralateral dissection after loss of IONM signal on the first side) and prognostication.3,6–9 These topics have garnered interest considering that
Rhinological and Otological Society, Inc.
Stimulation Threshold Greatly Affects the Predictive Value of Intraoperative Nerve Monitoring Daniel L. Faden, MD; Lisa A. Orloff, MD; Tokunbo Ayeni, BS; Daniel S. Fink, MD; Katherine Yung, MD Objectives/Hypothesis: Using a standardized, graded, intraoperative stimulation protocol, we aimed to delineate the effects of various stimulation levels applied to the recurrent laryngeal nerve on the postoperative predictive value of intraoperative nerve monitoring. Study Design: A total of 917 nerves at risk were included for analysis. Intraoperatively, patients underwent stimulation of the recurrent laryngeal nerve at 0.3, 0.5, 0.8, and 1.0 mA followed by postoperative laryngoscopy for correlation with intraoperative findings. Methods: Sensitivity, specificity, positive predictive value, and negative predictive value were calculated at each stimulation level. Results: Sensitivity, specificity, positive predictive value, and negative predicative values ranged from 100% to 37%, 6% to 99%, 2% to 39%, and 100% to 99%, respectively at 0.3 to 1.0 mA. No demographic variables affected sensitivity or specificity. Receiver operating characteristic analysis identified 0.5 mA as the level of stimulation that optimizes sensitivity and specificity. Conclusions: The predictive value of intraoperative nerve monitoring varies greatly depending on the stimulation levels used. At low amplitudes of stimulation, nerve monitoring has high sensitivity and negative predictive value but low specificity and positive predictive value, related to the high rate of false positives. At high levels of stimulation, specificity and negative predictive value are high, sensitivity is low, and the positive predictive value rises as the rate of false negatives increase and the rate of false positives decrease. A stimulation level of 0.5 mA optimizes the predictive value of nerve monitoring; however, stimulation at multiple levels significantly improves the predictive value of intraoperative nerve monitoring. Key Words: Recurrent laryngeal nerve, intraoperative nerve monitoring, thyroid surgery. Level of Evidence: 2b. Laryngoscope, 125:1265–1270, 2015
INTRODUCTION Surgery that puts the recurrent laryngeal nerve (RLN) at risk, including thyroidectomy, parathyroidectomy and central neck dissection, is on the rise in the United States as the population ages and the incidence of thyroid cancer increases.1 Although occurring in only about 3% of patients,2,3 damage to one or both RLNs can result in significant morbidity including voice changes, dysphagia, dyspnea, or airway distress, and need for tracheostomy or other interventions. Previously published
Additional Supporting Information may be found in the online version of this article. From the Department of Otolaryngology–Head and Neck Surgery (D.L.F., K.Y.) and School of Medicine (T.A.), University of California, San Francisco, San Francisco, California; Department of Otolaryngology– Head and Neck Surgery (L.A.O.), Stanford University, Stanford, California; and the Department of Otolaryngology–Head and Neck Surgery (D.S.F.), Louisiana State University Health Sciences Center, New Orleans, Louisiana, U.S.A. Editor’s Note: This Manuscript was accepted for publication September 15, 2014. Presented at the Triological Society 117th Annual Meeting at COSM, Las Vegas, Nevada, U.S.A., May 15–16, 2014. The authors have no funding, financial relationships, or conflicts of interest to disclose. * Send correspondence to Daniel Faden, MD, UCSF Department of Otolaryngology–Head and Neck Surgery, 2380 Sutter Street, First Floor, San Francisco, CA, 94115. E-mail: [email protected] DOI: 10.1002/lary.24960
Laryngoscope 125: May 2015
studies have not shown that use of intraoperative nerve monitoring (IONM) decreases the rate of injury to the RLN2,3; however, use of IONM has become increasingly widespread. In recent surveys, approximately 80% of otolaryngologists and 48% of general surgeons reported using IONM, and 44% of otolaryngologists and 31% of general surgeons use IONM routinely.4,5 More recently, interest has focused on the predictive value of IONM for intraoperative decision making (i.e., decision to proceed with contralateral dissection after loss of IONM signal on the first side) and prognostication.3,6–9 These topics have garnered interest considering that
