title: Extraocular muscle enlargement with tendon involvement in thyroid-associated orbitopathy.
abstract: OBJECTIVE
  To evaluate the configuration of extraocular muscle and tendon enlargement in patients with thyroid-associated orbitopathy (TAO).
  
  
  METHODS
  Retrospective, noncomparative case series.
  
  
  METHODS
  We retrospectively evaluated the preoperative computed tomography (CT) or magnetic resonance imaging (MRI) scans, or both, of 125 consecutive patients with previously diagnosed TAO. Axial CT (n = 88) or MRI (n = 37) slices of the orbits were examined for tendon involvement of enlarged medial or lateral recti muscles. A ratio of tendon to muscle width greater than 0.5 was considered as tendon involvement.
  
  
  RESULTS
  Eight patients (6.4%) with TAO demonstrated tendon involvement on axial CT or MRI. These patients had significantly greater diplopia in primary gaze than patients with no tendon involvement or patients with no muscle enlargement.
  
  
  CONCLUSIONS
  The configuration of extraocular muscle enlargement on imaging studies has traditionally been used to differentiate TAO from other inflammatory processes because the tendon is typically spared (fusiform configuration) in TAO. However, we found that the configuration of tendon involvement (cylindrical configuration) can occasionally be noted in TAO and may be more frequently associated with primary gaze diplopia. Tendon involvement does not eliminate the diagnostic possibility of TAO.
authors.affiliation: Division of Orbital and Ophthalmic Plastic Surgery, Department of Ophthalmology, Jules Stein Eye Institute, David Geffen School of Medicine, University of California at Los Angeles, 90095-7006, USA. simon@jsei.ucla.edu
authors.forename: Guy J
authors.initials: GJ
authors.lastname: Ben Simon
authors.forename: Hasan M
authors.initials: HM
authors.lastname: Syed
authors.forename: Raymond
authors.initials: R
authors.lastname: Douglas
authors.forename: John D
authors.initials: JD
authors.lastname: McCann
authors.forename: Robert A
authors.initials: RA
authors.lastname: Goldberg
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D004172:Diplopia / Q000175:diagnosis; D005260:Female; D006111:Graves Disease / Q000175:diagnosis*; D006801:Humans; D006984:Hypertrophy; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009801:Oculomotor Muscles / Q000473:pathology*; D012189:Retrospective Studies; D013710:Tendons / Q000473:pathology*; D014057:Tomography, X-Ray Computed