title: Magnetic resonance imaging criteria for distinguishing between inclusion body myositis and polymyositis.
abstract: OBJECTIVE
  To develop diagnostic imaging criteria for polymyositis (PM) and sporadic inclusion body myositis (sIBM).
  
  
  METHODS
  We investigated 220 patients with suspected inflammatory myopathies by magnetic resonance imaging (MRI). Findings were compared with the results of clinical and biological examinations and muscle biopsy. PM and IBM were diagnosed in 25 patients each. Quantitative and qualitative MRI analysis of the 3 muscle groups of the 2 thighs included fatty infiltration, atrophy, inflammation, and the type and distribution of the lesions.
  
  
  RESULTS
  MRI was abnormal in all patients. Fatty infiltration and atrophy were more frequent in patients with sIBM (p < 0.05). Inflammation as the sole abnormality was preferentially encountered in PM (p = 0.05). Widespread abnormalities were more frequent in sIBM (p < 0.01). Abnormalities in PM tended to be distributed along the fascia. Involvement of the anterior group, an asymmetrical distribution, and a distal predominance were all more frequent in sIBM (p < 0.001).
  
  
  CONCLUSIONS
  Despite some overlap in MRI findings between the 2 diseases, MRI was useful for distinguishing PM from sIBM.
authors.affiliation: Department of Radiology, Institute of Myology, Paris, France. elisabeth.dion@psl.ap-hop-paris.fr
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Dion
authors.forename: Patrick
authors.initials: P
authors.lastname: Cherin
authors.forename: Christine
authors.initials: C
authors.lastname: Payan
authors.forename: Jean-Charles
authors.initials: JC
authors.lastname: Fournet
authors.forename: Thomas
authors.initials: T
authors.lastname: Papo
authors.forename: Thierry
authors.initials: T
authors.lastname: Maisonobe
authors.forename: Eric
authors.initials: E
authors.lastname: Auberton
authors.forename: Olivier
authors.initials: O
authors.lastname: Chosidow
authors.forename: Pierre
authors.initials: P
authors.lastname: Godeau
authors.forename: Jean-Charles
authors.initials: JC
authors.lastname: Piette
authors.forename: Serge
authors.initials: S
authors.lastname: Herson
authors.forename: Philippe
authors.initials: P
authors.lastname: Grenier
mesh_terms: D000328:Adult; D000368:Aged; D001707:Biopsy, Needle; D016009:Chi-Square Distribution; D015331:Cohort Studies; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D018979:Myositis, Inclusion Body / Q000175:diagnosis / Q000473:pathology*; D017285:Polymyositis / Q000175:diagnosis / Q000473:pathology*; D011336:Probability; D011446:Prospective Studies; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D018709:Statistics, Nonparametric