title: Magnetic resonance imaging determination of extraocular eye muscle volume in patients with thyroid-associated ophthalmopathy and proptosis.
abstract: OBJECTIVE
  Recent studies concerning the association between extraocular muscle (EOM) enlargement in thyroid-associated ophthalmopathy (TAO) and immunological and clinical activity have not been conclusive, probably due to a lack of uniform imaging methods (ultrasonography, computer tomography [CT] or magnetic resonance imaging [MRI]) and difficulties in the determination of EOM volume. The aim of the present study was to examine the significance of EOM enlargement as established by MRI-based volume determination, with reference to proptosis and the presence of autoantibodies, clinical activity and the duration of active disease.
  
  
  METHODS
  We determined EOM volume using MRI in 15 patients concomitantly with the determination of TSH, thyroid hormones, thyrotropin receptor antibodies (TRab) thyroid peroxidase antibodies (TPOab) and clinical activity score (CAS) at entry. We also established the duration until cessation of clinically active TAO.
  
  
  RESULTS
  All 15 patients had bilateral EOM enlargement, but swelling of orbital fatty tissue was absent. Significant correlations between thickness of musculi rectales and proptosis, values of TRab, CAS, and duration of activity were observed.
  
  
  CONCLUSIONS
  Our results support the hypothesis of a role of thyrotropin receptor antibodies in the pathogenesis of TAO and suggest that only EOM enlargement is responsible for proptosis in TAO.
authors.affiliation: Department of Endocrinology, Esbjerg County Hospital, Esbjerg, Denmark. jan@kvetny.dk
authors.forename: Jan
authors.initials: J
authors.lastname: Kvetny
authors.forename: Katriina Bøcker
authors.initials: KB
authors.lastname: Puhakka
authors.forename: Lisbeth
authors.initials: L
authors.lastname: Røhl
mesh_terms: D000328:Adult; D013956:Antithyroid Agents / Q000627:therapeutic use; D001323:Autoantibodies / Q000097:blood; D005094:Exophthalmos / Q000175:diagnosis* / Q000188:drug therapy / Q000276:immunology; D005260:Female; D049970:Graves Ophthalmopathy / Q000175:diagnosis* / Q000188:drug therapy / Q000276:immunology; D006801:Humans; D006984:Hypertrophy; D007453:Iodide Peroxidase / Q000276:immunology; D008279:Magnetic Resonance Imaging; D008713:Methimazole / Q000627:therapeutic use; D009801:Oculomotor Muscles / Q000473:pathology*; D011989:Receptors, Thyrotropin / Q000276:immunology; D013963:Thyroid Hormones / Q000276:immunology; D013972:Thyrotropin / Q000276:immunology
chemical_list: D013956:Antithyroid Agents; D001323:Autoantibodies; D011989:Receptors, Thyrotropin; D013963:Thyroid Hormones; D008713:Methimazole; D013972:Thyrotropin; D007453:Iodide Peroxidase