Posterior cricoarytenoid muscle electrophysiologic changes are predictive of vocal cord paralysis with recurrent laryngeal nerve compressive injury in a canine model.
Injury to the recurrent laryngeal nerve (RLN) is a dreaded complication of endocrine surgery. Intraoperative neural monitoring (IONM) has been increasingly utilized to assess the functional status of the RLN. Although the posterior cricoarytenoid muscle (PCA) is innervated by the RLN as the abductor of the larynx, PCA electromyography (EMG) is infrequently recorded during IONM and PCA activity after RLN compressive injury remains poorly characterized.



Single-subject prospective animal study.



We employed a canine model to identify postcricoid EMG correlates of postoperative vocal cord paralysis (VCP). Postcricoid electrode recordings were obtained before and after compressive RLN injury associated with VCP.



Normative postcricoid recordings revealed mean amplitude of 1288 microvolt (μV) and latency of 8.2 millisecond (ms) with maximum (1 milliamp [mA]) vagal stimulation, and mean amplitude of 1807 μV and latency of 3.5 ms with maximum (1 mA) RLN stimulation. Following injury that was associated with VCP, there was 62.1% decrement in postcricoid EMG amplitude with maximum vagal stimulation and 80% decrement with maximum RLN stimulation. Threshold stimulation of the vagus increased by 23%, and there was a corresponding 42% decrease in amplitude. For RLN stimulation, latency increased by 17.3% following injury, whereas threshold stimulation increased by 61% with 35.5% decrement in EMG amplitude. Thus, if RLN amplitude decreases by ≥ 80%, with absolute amplitude of ≤ 300 μV or less and latency increase of ≥ 10%, RLN injury is likely associated with VCP.



Our results predict postoperative VCP based on postcricoid electromyographic IONM and may guide surgical decision making.



NA Laryngoscope, 126:2744-2751, 2016.
Division of Thyroid and Parathyroid Surgery, Department of Otolaryngology, Massachusetts Eye and Ear Infirmary and Harvard Medical School, Boston, Massachusetts, U.S.A.
Sidharth V
SV
Puram
Division of Thyroid and Parathyroid Surgery, Department of Otolaryngology, Massachusetts Eye and Ear Infirmary and Harvard Medical School, Boston, Massachusetts, U.S.A.
Harold
H
Chow
Division of Thyroid and Parathyroid Surgery, Department of Otolaryngology, Massachusetts Eye and Ear Infirmary and Harvard Medical School, Boston, Massachusetts, U.S.A.|Department of Otorhinolaryngology-Head and Neck Surgery, Kaohsiung Medical University Hospital; Faculty of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan.
Che-Wei
CW
Wu
Department of Surgery, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, U.S.A.
James T
JT
Heaton
Division of Thyroid and Parathyroid Surgery, Department of Otolaryngology, Massachusetts Eye and Ear Infirmary and Harvard Medical School, Boston, Massachusetts, U.S.A.
Dipti
D
Kamani
Division of Thyroid and Parathyroid Surgery, Department of Otolaryngology, Massachusetts Eye and Ear Infirmary and Harvard Medical School, Boston, Massachusetts, U.S.A.
Gautham
G
Gorti
Department of Otorhinolaryngology-Head and Neck Surgery, Kaohsiung Medical University Hospital; Faculty of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan.
Feng Yu
FY
Chiang
Department of Surgical Sciences and Human Morphology, Division of Surgery, University of Insubria-School of Medicine, Varese, Italy.
Gianlorenzo
G
Dionigi
Department of Endocrine Surgery, Jagiellonian University Medical College, Krakow, Poland.
Marcin
M
Barczynski
Department of General, Visceral, and Vascular Surgery, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany.
Rick
R
Schneider
Department of General, Visceral, and Vascular Surgery, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany.
Henning
H
Dralle
Department of General, Visceral, and Vascular Surgery, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany.
Kerstin
K
Lorenz
Division of Thyroid and Parathyroid Surgery, Department of Otolaryngology, Massachusetts Eye and Ear Infirmary and Harvard Medical School, Boston, Massachusetts, U.S.A.|Division of Surgical Oncology, Department of Surgery, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, U.S.A.
Gregory W
GW
Randolph
D000818:Animals; D004285:Dogs; D004576:Electromyography; D055724:Electrophysiological Phenomena; D005260:Female; D007821:Laryngeal Muscles / Q000294:innervation / Q000502:physiology*; D008297:Male; D023421:Models, Animal; D011183:Postoperative Complications / Q000503:physiopathology*; D011446:Prospective Studies; D012009:Recurrent Laryngeal Nerve / Q000503:physiopathology; D061226:Recurrent Laryngeal Nerve Injuries / Q000503:physiopathology*; D014826:Vocal Cord Paralysis / Q000503:physiopathology*
Recurrent laryngeal nerve; endocrine; injury; monitoring; postcricoid; thyroid surgery