Does Masseter Muscle Hypertrophy Affect the Etiology and Localization of Parotid Duct Stones?

This study investigated whether increased masseter muscle volume contributes to parotid sialolithiasis through extrinsic mechanical compression of Stensen's duct.

In this retrospective case-control study, 29 patients with parotid sialolithiasis who underwent sialendoscopy between 2018 and 2024 were compared with 35 age- and sex-matched controls without salivary gland disease. Demographic and anthropometric data, including body mass index (BMI), were recorded. Stone characteristics were assessed on computed tomography (CT), and bilateral masseter muscle volume (MMV) was measured using semi-automated tracing. Group comparisons, mixed-effects modeling, concordance analysis, and logistic regression were performed.

No significant between-group differences were observed in right, left, or average MMV. In sex-stratified analyses, male controls had significantly greater average MMV than male sialolithiasis patients (39.23 vs. 30.15 cm³; p = 0.015), whereas no significant difference was found among females. Intraindividual comparison of affected versus unaffected sides and concordance analysis between stone laterality and dominant masseter side showed no significant associations. BMI was significantly higher in the sialolithiasis group than in controls (27.13 vs. 24.02 kg/m²; p = 0.011) and was the only independent factor associated with parotid sialolithiasis.

Static MMV does not appear to be a primary determinant of parotid sialolithiasis. Although masseter-related effects on ductal geometry and drainage cannot be excluded, direct extrinsic compression by an enlarged masseter muscle is unlikely to represent a major pathophysiological mechanism. Future studies should incorporate dynamic ductal imaging, EMG-based functional assessment, and larger prospective cohorts.

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