Quantitative Assessment of Extrinsic Tongue Muscle Stiffness in Obstructive Sleep Apnea Using Shear Wave Elastography

<b>Background/Objectives:</b> This study aimed to quantitatively and noninvasively evaluate the changes in the Genioglossus (GG) and Geniohyoid (GH) muscles in patients with Obstructive Sleep Apnea (OSA) using ultrasonography (US) and shear wave elastography (SWE). <b>Methods:</b> This prospective study included 94 adults (18-73 years) who underwent polysomnography (27 normal; 67 OSA). GG and GH muscle thickness was measured with US, and stiffness with SWE. Participants were grouped as non-OSA (Group 0) and OSA (Group 1). OSA patients were further divided by apnea-hypopnea index (AHI) into mild, moderate, and severe (Groups 1-3), forming four groups including controls. <b>Results:</b> No significant differences were observed in genioglossus or geniohyoid muscle thickness between groups. Shear wave elastography revealed significantly higher stiffness values for both the genioglossus and geniohyoid muscles bilaterally in OSA patients compared with non-OSA individuals (approximately 2.7 m/s vs. 2.4-2.5 m/s, <i>p</i> < 0.01). Geniohyoid muscle stiffness on both sides increased progressively with OSA severity, with significantly higher values in severe compared with mild OSA (<i>p</i> < 0.05). In contrast, genioglossus stiffness did not differ significantly across OSA severity subgroups. <b>Conclusions</b>: In patients with OSA, GH and GG muscle thickness remains unchanged, but their stiffness measured by SWE increases. GH stiffness also rises with increasing disease severity. These results indicate that GG and GH muscle stiffness may serve as useful noninvasive markers for OSA.