title: CT scan evidence of dysthyroid optic neuropathy.
abstract: OBJECTIVE
  To determine the utility of CT imaging in identifying patients with dysthyroid optic neuropathy.
  
  
  METHODS
  Orbital CT scans of 12 randomly selected patients with dysthyroid optic neuropathy and 15 control subjects with Graves orbitopathy were retrospectively reviewed by two investigators blinded to the clinical data. The clinical diagnosis of optic neuropathy was made by one author before obtaining CT images and was based on clinical features.
  
  
  RESULTS
  Optic nerve crowding (P<0.001) and intracranial fat prolapse (P<0.05) were the imaging features independently related to optic neuropathy. A muscle index greater than 50% had excellent sensitivity (100%) but did not have high specificity (47%) for dysthyroid optic neuropathy. Superior ophthalmic vein dilation and proptosis did not show significant relations with optic neuropathy.
  
  
  CONCLUSIONS
  This study suggests that patients with Graves orbitopathy who have severe optic nerve crowding, intracranial fat prolapse, and/or muscle index greater than 50% present on orbital CT scans are more likely to have coexisting optic neuropathy.
authors.affiliation: College of Physicians and Surgeons, Columbia University, New York, New York, USA.
authors.forename: JoAnn A
authors.initials: JA
authors.lastname: Giaconi
authors.forename: Michael
authors.initials: M
authors.lastname: Kazim
authors.forename: Tae
authors.initials: T
authors.lastname: Rho
authors.forename: Charles
authors.initials: C
authors.lastname: Pfaff
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D004311:Double-Blind Method; D006111:Graves Disease / Q000000981:diagnostic imaging*; D006801:Humans; D008875:Middle Aged; D009801:Oculomotor Muscles / Q000000981:diagnostic imaging / Q000473:pathology; D009901:Optic Nerve Diseases / Q000000981:diagnostic imaging*; D009915:Orbit / Q000000981:diagnostic imaging / Q000473:pathology; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed