Stylomandibular tunnel widening versus narrowing: a useful tool in evaluating suprahyoid mass lesions.

AIM: To evaluate whether qualitative and quantitative assessments of stylomandibular tunnel asymmetry are useful in lesion localization and differentiation.

MATERIALS AND METHODS: The stylomandibular tunnel was measured in 60 control patients at CT to determine normal side-to-side variation. Twenty-one patients in the study group with suprahyoid neck masses were divided into two subgroups, those with widening and those with narrowing of the pathological side. Surgical and pathological findings in these subgroups were compared for site of origin and histology.

RESULTS: Stylomandibular tunnel diameters in the control group had a mean variation of 0.9 mm (range: 0-3 mm, SD: 0.83 mm). Two-tailed t-test yielded a p-value of 0.018 for a variation of 3 mm and this was chosen as the threshold for disease. The widened stylomandibular tunnel group all had parotid gland lesions extending into the pre-styloid parapharyngeal space. The narrowed stylomandibular tunnel group had adenopathy, schwannomas, and paragangliomas/glomus vagale tumours arising from the post-styloid parapharyngeal space.

CONCLUSION: Qualitative assessment for asymmetry of the stylomandibular tunnel surpass the 3 mm threshold for pathology. Widening of the stylomandibular tunnel is primarily from deep lobe parotid lesions extending into the pre-styloid parapharyngeal space. Narrowing of the stylomandibular tunnel can be from adenopathy, schwannomas, and paragangliomas arising from the post-styloid parapharyngeal space.