The hypoglossal nerve palsy involved by papillary thyroid carcinoma detected on 18F-FDG PET/MRI.

A 51-year-old woman with papillary thyroid cancer (PTC) complained of headache.Physical examination found the tongue derivation torightside. Fluorine-18-fluorodeoxyglucose positron emission tomography/magnetic resonance imaging (18F-FDG PET/MRI) detected a hypermetabolic soft-tissue mass in the right retropharyngeal carotid space, where the nasopharyngeal carotid segment of right hypoglossal nerve passing inferiorly. The musculature in the right side of tongue was inflammatory instead of fatty infiltration, with hyperintense on T2-weighted image and hypermetabolism on PET. These images together indicated the early phase of hypoglossal nerve palsy caused by PTC invasion.