title: Magnetic resonance imaging of skeletal muscles in sporadic inclusion body myositis.
abstract: OBJECTIVE
  To analyse whether MRI of upper and lower extremity muscles in a large patient group with sporadic IBM (sIBM) is of additional value in the diagnostic work-up of sIBM.
  
  
  METHODS
  Thirty-two sIBM patients were included. Magnetic resonance (MR) parameters evaluated in 68 muscles of upper and lower extremity were muscle atrophy, fatty infiltration and inflammation. These findings were correlated with disease duration, weakness and serum creatine kinase (sCK) levels.
  
  
  RESULTS
  Fatty infiltration was far more common than inflammation. Muscles most frequently infiltrated with fat were the flexor digitorum profundus (FDP), anterior muscles of the upper leg and all muscles of the lower leg, preferentially the medial part of the gastrocnemius. The rectus femoris was relatively spared compared with other quadriceps muscles as well as the adductors of the upper leg. Inflammation was common in general, but individually sparse, present in 78% of the patients with a median of two inflamed muscles per patient. A statistically significant correlation was found between the amount of fatty infiltration and disease severity, disease duration and sCK.
  
  
  CONCLUSIONS
  We provide a detailed description of the MRI in sIBM and show a distinct pattern of muscle involvement. Relatively severe affliction of the medial compartment of the gastrocnemius, combined with relative sparing of the rectus femoris or involvement of the FDP can be indicative of sIBM. MRI can contribute to the diagnosis in selected patients with clear clinical suspicion, but lacking the mandatory set of muscle biopsy features.
authors.affiliation: Department of Neurology, Leiden University Medical Center, J3-R166, PO Box 9600, 2300 RC, Leiden, The Netherlands. f.cox@lumc.nl
authors.forename: Fieke M
authors.initials: FM
authors.lastname: Cox
authors.forename: Monique
authors.initials: M
authors.lastname: Reijnierse
authors.forename: Carla S P
authors.initials: CS
authors.lastname: van Rijswijk
authors.forename: Axel R
authors.initials: AR
authors.lastname: Wintzen
authors.forename: Jan J
authors.initials: JJ
authors.lastname: Verschuuren
authors.forename: Umesh A
authors.initials: UA
authors.lastname: Badrising
mesh_terms: D000328:Adult; D000368:Aged; D015331:Cohort Studies; D005260:Female; D006801:Humans; D035002:Lower Extremity / Q000473:pathology; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D018908:Muscle Weakness / Q000473:pathology; D018482:Muscle, Skeletal / Q000473:pathology*; D009133:Muscular Atrophy / Q000473:pathology*; D018979:Myositis, Inclusion Body / Q000175:diagnosis* / Q000473:pathology; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D018709:Statistics, Nonparametric; D034941:Upper Extremity / Q000473:pathology