Evaluation of Internal Laryngeal Muscles Related to Phonation and theCompensatory Mechanism in Patients with Unilateral Vocal Cord ParalysisUsing 18F-Fluorodeoxyglucose-Positron Emission Tomography

Background and Objectives：Several studies have reported that 18F-fluorodeoxyglucose (FDG) uptake in positron emission tomography (PET) imaging is physiologically increased at the intact vocal cord in patients with unilateral vocal cord paralysis, which is explained by a compensatory mechanism of the intact vocal cord. We aimed to evaluate internal laryngeal muscles related to phonation and the compensatory mechanism in patients with unilateral vocal cord paralysis. Subjects and Method： We performed 18FDG-PET imaging and neck computed tomography (CT) scan in the normal control group composed of 13 subjects and the paralyzed group composed of 11 patients with unilateral vocal cord paralysis. The two groups were divided into two groups, phonating and silent, before performing 18FDG-PET. 18FDG-PET and neck CT images by Syntegra. A specialist in nuclear medicine performed all the test measurements, the standardized uptake value (SUV) in the interarytenoid muscle (IA), both thyroarytenoid muscles (TA), and both lateral cricoarytenoid muscles (LCA). The mean SUVs were statistically analyzed. Results：In the Normal-Phonating group, the mean SUV of IA was the highest, with 3.68±0.96 (Mean±SD), followed by that of LCA, with 2.34±0.67. However, when compared with the same muscles in the Phonating-Silent group, only the SUV of IA was significantly increased by phonation. In the Paralyzed-Silent group, the SUV of TA in the intact side was the highest, with 2.30±0.39. In the Paralyzed-Phonating group, the SUV of TA in the intact side, IA, and LCA in the intact side were 5.88±2.65, 3.92±1.65, and 3.87±1.37, respectively. When compared with the same muscles in the Phonating-Silent group, the SUVs of TA and IA were significantly increased. Conclusion：The muscle related to the compensatory mechanism in patients with unilateral vocal cord paralysis is thyroarytenoid muscle in the intact side. The interarytenoid muscle plays a major role in the mechanism of phonation in humans.