Hypoglossal canal lesions: Distinctive imaging features and simple diagnostic algorithm

OBJECTIVE. The objective of this study is to compare the prevalence of hypoglossal canal lesions and identify differentiating imaging features. MATERIALS AND METHODS. A 15-year retrospective review of lesions of the hypoglossal nerve and hypoglossal canal, excluding those in patients with metastasis or prior head and neck cancer and those treated with radiation or surgery, was performed. Clinical fndings and lesion imaging features were documented. The contrast-enhanced T1-weighted nonenhancing cystic component of hypoglossal schwannomas was compared with size-matched pathologically proven vestibular schwannomas. RESULTS. Our review identifed 40 lesions encroaching on the hypoglossal canal, located within the hypoglossal canal, or found in both locations: 16 hypoglossal schwannomas, 15 juxtaarticular cysts, and nine purely cystic hypoglossal canal lesions. Hypoglossal schwannomas, which were intradural when involving the premedullary cistern, most commonly enhanced heterogeneously, with a thick peripheral enhancing component, a central enhancing component, or both enhancing components. Juxtaarticular cysts encroaching on the hypoglossal canal were extradural, were contiguous with a craniocervical junction synovial joint, and showed thin rim enhancement. Hypoglossal canal nonenhancing cystic lesions were confned to the hypoglossal canal, had signal intensity equivalent to CSF, and lacked any contrast enhancement. CONCLUSION. Although hypoglossal schwannomas, juxtaarticular cysts, and hypoglossal canal nonenhancing cystic lesions may all encroach on or lie within the hypoglossal canal, purely cystic lesions are unlikely to be schwannomas. A diagnostic algorithm applying key imaging and clinical fndings allows differentiation of these lesions, which have vastly different treatment regimens.