Whitney Liddy1,2, Samuel R Barber1, Matteo Cinquepalmi1,3, Brian M Lin1,2, Stephanie Patricio1, Natalia Kyriazidis1, Carlo Bellotti3, Dipti Kamani1,2, Sadhana Mahamad1, Henning Dralle4, Rick Schneider4, Gianlorenzo Dionigi5, Marcin Barczynski6, Che-Wei Wu7, Feng Yu Chiang7,8, Gregory Randolph1,2. 1. Division of Thyroid and Parathyroid Endocrine Surgery, Department of Otolaryngology, Massachusetts Eye and Ear Infirmary, Boston, Massachusetts, U.S.A. 2. Department of Otology and Laryngology, Harvard Medical School, Boston, Massachusetts, U.S.A. 3. Surgery of Thyroid and Parathyroid Operative Unit, Sapienza University of Rome, S. Andrea Hospital, Rome, Italy. 4. Department of General, Visceral, and Vascular Surgery, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany. 5. Endocrine Surgery Research Center, Department of Surgical Sciences, University of Insubria, Varese, Italy. 6. Department of Endocrine Surgery, Jagiellonian University College of Medicine, Krakow, Poland. 7. Department of Otorhinolaryngology-Head and Neck Surgery, Kaohsiung Medical University Hospital, Faculty of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan. 8. Institute of Clinical Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan.
Abstract
OBJECTIVES/HYPOTHESIS: Correlation of physiologically important electromyographic (EMG) waveforms with demonstrable muscle activation is important for the reliable interpretation of evoked waveforms during intraoperative neural monitoring (IONM) of the vagus nerve, recurrent laryngeal nerve (RLN), and external branch of the superior laryngeal nerve (EBSLN) in thyroid surgery. STUDY DESIGN: Retrospective chart review. METHODS: Data were reviewed retrospectively for thyroid surgery patients with laryngeal nerve IONM from January to December, 2015. EMG responses to monopolar stimulation of the vagus/RLN and EBSLN were recorded in bilateral vocalis, cricothyroid (CTM), and strap muscles using endotracheal tube-based surface and intramuscular hook electrodes, respectively. Target muscles for vagal/RLN and EBSLN stimulation were the ipsilateral vocalis and CTM, respectively. All other recording channels were nontarget muscles. RESULTS: Fifty surgical sides were identified in 37 subjects. All target muscle mean amplitudes were significantly higher than in nontarget muscles. With vagal/RLN stimulation, target ipsilateral vocalis mean amplitude was 1,095.7 μV (mean difference range = -814.1 to -1,078 μV, P < .0001). For EBSLN stimulation, target ipsilateral CTM mean amplitude was 6,379.3 μV (mean difference range = -6,222.6 to -6,362.3 μV, P < .0001). Target muscle large-amplitude EMG responses correlated with meaningful visual or palpable muscular responses, whereas nontarget EMG responses showed no meaningful muscle activation. CONCLUSIONS: Target and nontarget laryngeal muscles are differentiated based on divergence of EMG response directly correlating with presence or absence of visual and palpable muscle activation. Low-amplitude EMG waveforms in nontarget muscles with neural stimulation can be explained by the concept of far-field artifactual waveforms and do not correspond to a true muscular response. The surgeon should be aware of these nonphysiologic waveforms when interpreting and applying IONM during thyroid surgery. LEVEL OF EVIDENCE: 4 Laryngoscope, 127:764-771, 2017.
OBJECTIVES/HYPOTHESIS: Correlation of physiologically important electromyographic (EMG) waveforms with demonstrable muscle activation is important for the reliable interpretation of evoked waveforms during intraoperative neural monitoring (IONM) of the vagus nerve, recurrent laryngeal nerve (RLN), and external branch of the superior laryngeal nerve (EBSLN) in thyroid surgery. STUDY DESIGN: Retrospective chart review. METHODS: Data were reviewed retrospectively for thyroid surgery patients with laryngeal nerve IONM from January to December, 2015. EMG responses to monopolar stimulation of the vagus/RLN and EBSLN were recorded in bilateral vocalis, cricothyroid (CTM), and strap muscles using endotracheal tube-based surface and intramuscular hook electrodes, respectively. Target muscles for vagal/RLN and EBSLN stimulation were the ipsilateral vocalis and CTM, respectively. All other recording channels were nontarget muscles. RESULTS: Fifty surgical sides were identified in 37 subjects. All target muscle mean amplitudes were significantly higher than in nontarget muscles. With vagal/RLN stimulation, target ipsilateral vocalis mean amplitude was 1,095.7 μV (mean difference range = -814.1 to -1,078 μV, P < .0001). For EBSLN stimulation, target ipsilateral CTM mean amplitude was 6,379.3 μV (mean difference range = -6,222.6 to -6,362.3 μV, P < .0001). Target muscle large-amplitude EMG responses correlated with meaningful visual or palpable muscular responses, whereas nontarget EMG responses showed no meaningful muscle activation. CONCLUSIONS: Target and nontarget laryngeal muscles are differentiated based on divergence of EMG response directly correlating with presence or absence of visual and palpable muscle activation. Low-amplitude EMG waveforms in nontarget muscles with neural stimulation can be explained by the concept of far-field artifactual waveforms and do not correspond to a true muscular response. The surgeon should be aware of these nonphysiologic waveforms when interpreting and applying IONM during thyroid surgery. LEVEL OF EVIDENCE: 4 Laryngoscope, 127:764-771, 2017.
Authors: Alessandra Cossa; Giorgio Castagnola; Gherardo Romeo; Marco Bellucci; Giuseppe Nigri; Carlo Bellotti Journal: Endocrine Date: 2020-05-19 Impact factor: 3.633