title: Magnetic resonance imaging and ultrasound measurements of extraocular muscles in thyroid-associated ophthalmopathy at different stages of the disease.
abstract: OBJECTIVE
  To assess extraocular muscle (EOM) involvement in thyroid-associated orbitopathy (TAO) of different stages with magnetic resonance imaging (MRI) and ultrasound techniques.
  
  
  METHODS
  A total of 32 patients with TAO were divided into three groups according to whether they had mild active, pronounced active or longstanding inactive disease. Six patients with Graves' disease but no clinical signs of TAO and 10 healthy control subjects were also studied. Muscle volume and cross-sectional area were measured with MRI. A-scan ultrasound was used to measure muscle thickness.
  
  
  RESULTS
  The average MRI volume and maximal cross-sectional area of the EOM were significantly larger in patients with pronounced active and longstanding inactive TAO than in control subjects. Increased average muscle thickness measured by ultrasound was found mainly in patients with longstanding disease. Muscle enlargement was seen with MRI and ultrasound in individual patients in all patient groups, including those with Graves' disease but no TAO. Bilateral muscle enlargement was revealed by MRI in about two-thirds of patients with mild active TAO and in all patients with pronounced active and longstanding inactive TAO. Bilateral involvement estimated with ultrasound was less common in all patient groups. The MRI and ultrasound findings were not well correlated in any patient group.
  
  
  CONCLUSIONS
  Extraocular muscle enlargement was seen in all patient groups with TAO of differing levels of severity. Measurements with MRI of muscle volume or maximal cross-sectional area are considered good indicators of muscle enlargement in TAO.
authors.affiliation: Department of Ophthalmology, St Erik's Eye Hospital, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Gunnar
authors.initials: G
authors.lastname: Lennerstrand
authors.forename: Suna
authors.initials: S
authors.lastname: Tian
authors.forename: Bengt
authors.initials: B
authors.lastname: Isberg
authors.forename: Irene
authors.initials: I
authors.lastname: Landau Högbeck
authors.forename: Roberto
authors.initials: R
authors.lastname: Bolzani
authors.forename: Leif
authors.initials: L
authors.lastname: Tallstedt
authors.forename: Hermann
authors.initials: H
authors.lastname: Schworm
mesh_terms: D001837:Body Weights and Measures; D005260:Female; D049970:Graves Ophthalmopathy / Q000145:classification / Q000175:diagnosis*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009801:Oculomotor Muscles / Q000000981:diagnostic imaging* / Q000473:pathology*; D014463:Ultrasonography