Manifestations of Oral Muscle Mass, Tongue Strength, and Endurance in Patients with Stroke Across Varying Degrees of Swallowing Function: A Pilot Study

Background Post-stroke dysphagia (PSD) is associated with swallowing muscle atrophy and impaired tongue performance. Objectives This study aimed to compare oral muscle mass, muscle elasticity, and tongue performance in stroke patients with different swallowing function levels. Methods In this cross-sectional pilot study, 41 stroke patients from Kaohsiung Chang Gung Memorial Hospital, Taiwan, were stratified into three groups based on the Functional Oral Intake Scale (FOIS): severe dysphagia (levels 1–3), mild-to-moderate dysphagia (levels 4–6), and no dysphagia (level 7). Tongue and bilateral masseter muscle thickness and elasticity, expressed as shear wave velocity (SWV), were assessed using ultrasonography and sonoelastography. Tongue strength and endurance were evaluated using Iowa Oral Performance Instrument (IOPI). Group differences were analyzed using the Kruskal—Wallis test followed by Mann—Whitney U post hoc comparisons. Associations between FOIS scores and IOPI or sonographic measurements were evaluated using Spearman's rank correlation. Results Twenty-seven men and fourteen women were included. Unaffected-side masseter muscle thickness differed significantly among groups ( p < 0.05), increasing with better swallowing function. Tongue SWV was highest in the severe dysphagia group (median 1.98 [IQR 0.83] m/s), with significant differences among groups ( p < 0.05). Higher FOIS levels were associated with greater tongue strength and endurance, although endurance did not differ between the mild-to-moderate dysphagia and non-dysphagic groups. Conclusions Oral muscle mass measurements alone may not adequately reflect PSD severity. Integrating sonoelastography and IOPI assessments identifies increased tongue stiffness and reduced tongue performance in severe PSD, supporting severity-specific rehabilitation strategies.