Che-Wei Wu1, Feng-Yu Chiang1, Gregory W Randolph2,3, Gianlorenzo Dionigi4, Hoon Yub Kim5, Yi-Chu Lin1, Hui-Chun Chen6, Hsiu-Ya Chen7, Dipti Kamani2, Tsung-Yi Tsai1, I-Cheng Lu7, Pi-Ying Chang7. 1. 1 Department of Otolaryngology-Head and Neck Surgery, Kaohsiung Municipal Hsiao-Kang Hospital, Kaohsiung Medical University Hospital, Faculty of Medicine, College of Medicine, Kaohsiung Medical University , Kaohsiung, Taiwan . 2. 2 Division of Thyroid and Parathyroid Endocrine Surgery, Department of Otolaryngology, Massachusetts Eye and Ear Infirmary, Harvard Medical School , Boston, Massachusetts. 3. 3 Division of Surgical Oncology, Department of Surgery, Massachusetts General Hospital , Harvard Medical School, Boston, Massachusetts. 4. 4 Division for Endocrine and Minimally Invasive Surgery, Department of Human Pathology in Adulthood and Childhood "G. Barresi," University Hospital G. Martino, University of Messina , Sicily, Italy . 5. 5 Department of Surgery, Korea University College of Medicine , Seoul, Korea. 6. 6 Department of Nursing, Kaohsiung Medical University Hospital, Kaohsiung Medical University , Kaohsiung, Taiwan . 7. 7 Department of Anesthesiology, Kaohsiung Municipal Ta-Tung Hospital, Kaohsiung Municipal Hsiao-Kang Hospital, Kaohsiung Medical University Hospital, Faculty of Medicine, College of Medicine, Kaohsiung Medical University , Kaohsiung, Taiwan .
Abstract
BACKGROUND: Intraoperative neural monitoring (IONM) has gained widespread acceptance as an adjunct to the gold standard of visual identification of the recurrent laryngeal nerve (RLN) during thyroid surgery. Currently, laryngeal electromyography (EMG) recording during IONM is almost always performed using endotracheal tube (ETT) surface electrodes placed adjacent to vocal folds originating from the inner surface of the thyroid cartilage (TC). Therefore, it was hypothesized that surface recording electrodes placed on the outer surface of the TC should enable access to the EMG response of the vocal folds during IONM. The aim of this experimental study was to evaluate the feasibility of the transcartilage approach for laryngeal EMG recording during IONM. METHODS: A porcine model (12 pigs and 24 RLN sides) with well established applicability in IONM research was used for the experiments. Both ETT electrodes adjacent to vocal folds and adhesive pre-gelled electrodes on the TC were used for EMG recording during IONM. Electrically evoked EMG signals detected by both electrode types were recorded and analyzed. EMG changes during tracheal displacement and RLN traction injury were compared. RESULTS: Both the ETT and TC recording electrodes recorded typical laryngeal EMG waveforms evoked by a 1 mA stimulus current applied on both sides of the RLNs and vagus nerves (VNs). Under RLN stimulation, the mean EMG amplitudes recorded with the ETT and TC electrodes were 973 ± 79 μV and 695 ± 150 μV, respectively. Under VN stimulation, the mean amplitudes were 841 ± 163 μV and 607 ± 162 μV, respectively. When upward displacement of the trachea was experimentally induced, the TC electrodes showed less variation in recorded EMG signals compared to ETT electrodes. When RLN traction stress was experimentally induced, both the ETT and TC electrodes accurately recorded the typical EMG pattern of progressively degrading amplitude and gradual recovery after release of traction. CONCLUSIONS: This study confirms the feasibility of using transcartilage surface electrodes for recording laryngeal EMG signals evoked during IONM in an animal model. However, before practical application of this approach in clinical thyroid surgery, further studies are needed to improve electrode designs by optimizing their shapes and sizes, and increasing their adhesive stability and sensitivity.
BACKGROUND: Intraoperative neural monitoring (IONM) has gained widespread acceptance as an adjunct to the gold standard of visual identification of the recurrent laryngeal nerve (RLN) during thyroid surgery. Currently, laryngeal electromyography (EMG) recording during IONM is almost always performed using endotracheal tube (ETT) surface electrodes placed adjacent to vocal folds originating from the inner surface of the thyroid cartilage (TC). Therefore, it was hypothesized that surface recording electrodes placed on the outer surface of the TC should enable access to the EMG response of the vocal folds during IONM. The aim of this experimental study was to evaluate the feasibility of the transcartilage approach for laryngeal EMG recording during IONM. METHODS: A porcine model (12 pigs and 24 RLN sides) with well established applicability in IONM research was used for the experiments. Both ETT electrodes adjacent to vocal folds and adhesive pre-gelled electrodes on the TC were used for EMG recording during IONM. Electrically evoked EMG signals detected by both electrode types were recorded and analyzed. EMG changes during tracheal displacement and RLN traction injury were compared. RESULTS: Both the ETT and TC recording electrodes recorded typical laryngeal EMG waveforms evoked by a 1 mA stimulus current applied on both sides of the RLNs and vagus nerves (VNs). Under RLN stimulation, the mean EMG amplitudes recorded with the ETT and TC electrodes were 973 ± 79 μV and 695 ± 150 μV, respectively. Under VN stimulation, the mean amplitudes were 841 ± 163 μV and 607 ± 162 μV, respectively. When upward displacement of the trachea was experimentally induced, the TC electrodes showed less variation in recorded EMG signals compared to ETT electrodes. When RLN traction stress was experimentally induced, both the ETT and TC electrodes accurately recorded the typical EMG pattern of progressively degrading amplitude and gradual recovery after release of traction. CONCLUSIONS: This study confirms the feasibility of using transcartilage surface electrodes for recording laryngeal EMG signals evoked during IONM in an animal model. However, before practical application of this approach in clinical thyroid surgery, further studies are needed to improve electrode designs by optimizing their shapes and sizes, and increasing their adhesive stability and sensitivity.
Authors: Sam Van Slycke; K Van Den Heede; K Magamadov; N Brusselaers; H Vermeersch Journal: Langenbecks Arch Surg Date: 2019-11-20 Impact factor: 3.445