Sidharth V Puram1, Harold Chow1, Che-Wei Wu1,2, James T Heaton3, Dipti Kamani1, Gautham Gorti1, Feng Yu Chiang2, Gianlorenzo Dionigi4, Marcin Barczyński5, Rick Schneider6, Henning Dralle6, Kerstin Lorenz6, Gregory W Randolph1,7. 1. Division of Thyroid and Parathyroid Surgery, Department of Otolaryngology, Massachusetts Eye and Ear Infirmary and Harvard Medical School, Boston, Massachusetts. 2. Department of Otorhinolaryngology-Head and Neck Surgery, Kaohsiung Medical University Hospital, Faculty of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan. 3. Department of Surgery, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts. 4. Department of Surgical Sciences and Human Morphology, Division of Surgery, University of Insubria - School of Medicine, Varese, Italy. 5. Department of Endocrine Surgery, Jagiellonian University Medical College, Krakow, Poland. 6. Department of General, Visceral, and Vascular Surgery, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany. 7. Division of Surgical Oncology, Department of Surgery, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts.
Abstract
BACKGROUND: Recurrent laryngeal nerve (RLN) injury is a known complication of thyroid/parathyroid surgery. Intraoperative nerve monitoring (IONM) has been used to gain more information regarding the functional status of the RLN intraoperatively; however, the electromyography (EMG) parameters of RLN after nontransection neuropraxic compressive injury remain unknown. METHODS: We developed a canine model to identify IONM EMG correlates of postoperative vocal cord paralysis (VCP) using a standardized method to simulate surgical RLN compression sufficient to cause VCP. RESULTS: Compression nerve injury decreased EMG amplitude and increased EMG latency, with a 60% increase in RLN threshold stimulation compared to preinjury values. If RLN amplitude decreases by 80% with an absolute amplitude of 300 μV or less in combination with a latency increase of 10% or more, then nerve injury and associated VCP is likely. CONCLUSION: These results may help surgeons to prognosticate postoperative neural function and intraoperative decision-making regarding contralateral thyroid surgery.
BACKGROUND: Recurrent laryngeal nerve (RLN) injury is a known complication of thyroid/parathyroid surgery. Intraoperative nerve monitoring (IONM) has been used to gain more information regarding the functional status of the RLN intraoperatively; however, the electromyography (EMG) parameters of RLN after nontransection neuropraxic compressive injury remain unknown. METHODS: We developed a canine model to identify IONM EMG correlates of postoperative vocal cord paralysis (VCP) using a standardized method to simulate surgical RLN compression sufficient to cause VCP. RESULTS:Compression nerve injury decreased EMG amplitude and increased EMG latency, with a 60% increase in RLN threshold stimulation compared to preinjury values. If RLN amplitude decreases by 80% with an absolute amplitude of 300 μV or less in combination with a latency increase of 10% or more, then nerve injury and associated VCP is likely. CONCLUSION: These results may help surgeons to prognosticate postoperative neural function and intraoperative decision-making regarding contralateral thyroid surgery.