title: Hypoglossal nerve palsy missed and misinterpreted:  the hidden skull base.
abstract: OBJECTIVE
  Dysarthria and tongue swelling may be seen with hypoglossal nerve palsy, and on cross-sectional imaging studies, tongue denervation can be misinterpreted as a primary base-of-tongue mass. Understanding radiological patterns of tongue denervation is important to prevent misinterpretation. Close evaluation of the skull base is critical as hypoglossal palsies resulting from pathology here are often overlooked.
  
  
  METHODS
  Neck and brain magnetic resonance imaging studies obtained in 7 adult patients referred to our institution with clinically and/or radiologically suspected tongue base masses were retrospectively reviewed. Outside imaging evaluations were misinterpreted as base-of-tongue tumors in 3 patients, incorrectly read as normal in 2, and skull base pathologies were missed in 5.
  
  
  RESULTS
  All 7 patients showed magnetic resonance imaging findings typical of tongue denervation: T2-weighted hyperintensity of involved hemitongue, protrusion of the tongue into oropharynx, variable fatty infiltration. All 5 skull base masses involved hypoglossal canal (4 metastases, 1 multiple myeloma; 4 newly diagnosed cancers). Two patients had internal carotid artery dissections at the skull base.
  
  
  CONCLUSIONS
  To avoid misinterpretation of tongue denervation for tongue base mass, understanding of tongue innervations and classic imaging findings of hypoglossal denervation are essential. Careful inspection of skull base is paramount to avoid overlooking these hidden pathologies.
authors.affiliation: Division of Neuroradiology, Department of Radiology, University of Pennsylvania School of Medicine, Philadelphia, PA, USA.
authors.forename: Kim O
authors.initials: KO
authors.lastname: Learned
authors.forename: Erica R
authors.initials: ER
authors.lastname: Thaler
authors.forename: Bert W
authors.initials: BW
authors.lastname: O'Malley
authors.forename: M Sean
authors.initials: MS
authors.lastname: Grady
authors.forename: Laurie A
authors.initials: LA
authors.lastname: Loevner
mesh_terms: D000328:Adult; D000368:Aged; D020215:Carotid Artery, Internal, Dissection / Q000150:complications / Q000175:diagnosis* / Q000473:pathology; D003287:Contrast Media; D003937:Diagnosis, Differential; D003951:Diagnostic Errors; D038524:Diffusion Magnetic Resonance Imaging; D017352:Echo-Planar Imaging / Q000379:methods; D005260:Female; D005682:Gadolinium; D006801:Humans; D007002:Hypoglossal Nerve / Q000473:pathology; D020437:Hypoglossal Nerve Diseases / Q000150:complications* / Q000175:diagnosis / Q000473:pathology; D007089:Image Enhancement; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D019291:Skull Base / Q000473:pathology; D019292:Skull Base Neoplasms / Q000150:complications / Q000175:diagnosis* / Q000473:pathology; D014059:Tongue / Q000294:innervation / Q000473:pathology
chemical_list: D003287:Contrast Media; D005682:Gadolinium