title: Hypoglossal nerve palsy in nasopharyngeal carcinoma.
abstract: BACKGROUND
  The aim of the study was to use magnetic resonance (MR) imaging to determine the cause of hypoglossal nerve palsy and the sites of injury in patients with nasopharyngeal carcinoma before radiation therapy and during postradiation therapy follow-up.
  
  
  METHODS
  The clinical records and MR studies of 21 patients with hypoglossal nerve palsy were retrospectively studied. These 21 patients belonged to a cohort of 387 patients with nasopharyngeal carcinoma (153 with newly diagnosed disease and 234 on postradiation follow-up) who underwent MR imaging in a 2.5-year period.
  
  
  RESULTS
  Four patients had hypoglossal nerve palsy at initial diagnosis and all of them had extensive skull base invasion from tumor extending postero-inferiorly to the level of the foramen magnum. The nerve was invaded in the carotid sheath (3), hypoglossal nerve canal (3), and premedullary cistern (1). In 17 patients developing hypoglossal nerve palsy after radiotherapy, only two (12%) had evidence of tumor recurrence. Radiation-induced neuropathy was the probable cause in 14 patients and 1 case was judged indeterminate. MR evidence of fibrosis was demonstrable along the course the nerve in four patients (29%), involving the carotid sheath (4), hypoglossal nerve canal (2), and premedullary cistern (1). No patient had MR evidence of radiation change in the brain stem. Seven patients had a history of a boost dose of radiation to the parapharyngeal region on one or both sides, and nerve palsy occurred on the boosted side in six of them.
  
  
  CONCLUSIONS
  Hypoglossal nerve palsy on presentation was caused by locally advanced nasopharyngeal tumor whereas a palsy arising after radiation therapy was more frequently caused by postradiation damage rather than cancer.
authors.affiliation: Department of Diagnostic Radiology and Organ Imaging, Faculty of Medicine, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, New Territories, Hong Kong.
authors.forename: A D
authors.initials: AD
authors.lastname: King
authors.forename: S F
authors.initials: SF
authors.lastname: Leung
authors.forename: P
authors.initials: P
authors.lastname: Teo
authors.forename: W W
authors.initials: WW
authors.lastname: Lam
authors.forename: Y L
authors.initials: YL
authors.lastname: Chan
authors.forename: C
authors.initials: C
authors.lastname: Metreweli
mesh_terms: D000230:Adenocarcinoma / Q000503:physiopathology / Q000532:radiotherapy*; D000328:Adult; D000368:Aged; D004307:Dose-Response Relationship, Radiation; D005260:Female; D006801:Humans; D007002:Hypoglossal Nerve / Q000473:pathology / Q000528:radiation effects*; D020437:Hypoglossal Nerve Diseases / Q000175:diagnosis / Q000453:epidemiology / Q000209:etiology*; D015994:Incidence; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009303:Nasopharyngeal Neoplasms / Q000503:physiopathology / Q000532:radiotherapy*; D010243:Paralysis / Q000175:diagnosis / Q000453:epidemiology / Q000209:etiology; D011379:Prognosis; D011832:Radiation Injuries / Q000175:diagnosis / Q000453:epidemiology / Q000209:etiology*; D011878:Radiotherapy / Q000009:adverse effects*; D011879:Radiotherapy Dosage; D012189:Retrospective Studies; D018570:Risk Assessment