J Rheum Dis.  2013 Oct;20(5):297-302. 10.4078/jrd.2013.20.5.297.

The Utility of Magnetic Resonance Imaging in Inflammatory Myopathy

• Kim JJ
• Lee SH
• Paik SS
• Yoo DH

• KMID: 2223005
• DOI: http://doi.org/10.4078/jrd.2013.20.5.297

Abstract

OBJECTIVE
The idiopathic inflammatory myopathies (IIMs) are chronic systemic connective tissue diseases. The muscle biopsy is a definitive diagnostic tool but blind biopsy sometimes produces to negative results. Magnetic resonance imaging (MRI) as a tool for early diagnosis, guidance for biopsy, assessing extent of lesions and monitoring therapy in IIMs has been reported. The aim of this study is to assess the association of thigh inflammation through MRI and biopsy specimens with clinical findings.
METHODS
Sixty patients diagnosed with dermatomyositis (DM) or polymyositis (PM) from 2004 to 2011 in one center of rheumatology were enrolled. We reviewed clinical, laboratory, histopathologic and MRI of thigh data at initial diagnosis. The inflammation grades by MRI and histopathology of muscles were evaluated through 4-point scoring systems.
RESULTS
The laboratory findings for aldolase and CK differed significantly between DM patients (68.3%) and PM patients (31.7%). Fasciitis was detected by MRI in 43.3% of patients, of whom 88.5% had DM (p<0.05). The fasciitis was also associated with myalgia (p<0.05). Almost all MRI findings were symmetric except for two patients. The mean of total signal intensity was higher in patients with decreased muscle power. The signal intensity of affected muscle was slightly associated with muscle enzymes and histopathologic grading.
CONCLUSION
Fasciitis was observed more in DM patients. MRI findings were associated with muscle enzymes and histopathologic grading. Signal intensity on MRI may be useful for measurement of disease activity in acute IIMs. The noninvasive nature and high sensitivity of muscle inflammation suggest that MRI images should be considered prior to muscle biopsy and treatment of IIMs.

Keyword

Inflammatory myopathy; MRI

MeSH Terms

Biopsy
Connective Tissue Diseases
Dermatomyositis
Early Diagnosis
Fasciitis
Fructose-Bisphosphate Aldolase
Humans
Inflammation
Magnetic Resonance Imaging*
Magnetics*
Magnets*
Muscles
Myositis*
Polymyositis
Rheumatology
Thigh
Fructose-Bisphosphate Aldolase

Figure

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  Figure 1. The signal intensity at STIR magnetic resonance imaging (MRI) of transaxial section. No signal intensity (arrowhead on Biceps femoris), subtle signal intensity (short narrow arrow on Semimembranous) were represented for score 0 and 1, respectively. Focal signal intensity (long narrow arrow on Vastus intermedialis) in each muscle which was affected less than 50% of area was represented for score 2. Diffuse signal intensity (wide arrow on Gracilis) was represented for score 3.

• 

  Figure 2. Fasciitis on STIR magnetic resonance imaging of transaxial section in a dermatomyositis patient with myalgia symptom for 5 months until diagnosis. Areas of high signal intensity (arrows) observed in the fascias surrounding the Sartorius, Vastus intermedialis, Gracilis, Semimembranosus and Semitendinosus muscles.

• 

  Figure 3. Difference of total signal intensity depending on muscle power. Decreased muscle power MRC grade 0-IV, Normal muscle power MRC grade V.

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  Figure 4. Scatter plots of histopathologic scoring with MRI findings at biopsied muscles. Histopathologic scoring showed slightly positive correlations with signal intensity (r=0.339, p<0.05) (A) and edema portion (r=0.381, p<0.05) (B), and slightly negative correlation with atrophy portion (r=−0.311, p<0.05) (C) at the biopsied muscles.

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