J Korean Rheum Assoc.  2002 Sep;9(3):159-168.

Clinical Implication of Magnetic Resonance Imaging in the Idiopathic Inflammatory Myopathies

• Koh JH
• Hong SJ
• Ahn HJ
• Ahn JK
• Jeon CH
• Cha HS
• Ahn JM
• Kim HS
• Seo YL
• Koh EM

Abstract

OBJECTIVE
The purpose of the study is to describe the magnetic resonance imaging (MRI) findings and to investigate useful sequences of MRI in inflammatory myopathies. A third goal is to correlate MRI findings with the grade of histopathologic severity.
METHODS
Sixteen patients (13 women, 3 men), aged 21-74 years (median age of 49) with inflammatory myositis (examined with both MRI and muscle biopsy) were studied. Ten patients were diagnosed with polymyositis and 6 with dermatomyositis. Conventional T1-weighted (SE 366/12) and T2-weighted (SE 4766/90) fast spin-echo and fat-suppressed T1-weighted MR images with contrast enhancement (FSAT T1 CE) were obtained. Ratios between the signal intensities of a muscle and the signal intensities of subcutaneous fat in the same tomographic sections were calculated to objectively represent the degree of signal intensities. Semi-quantitative grading of severities in muscle biopsy specimen was examined based on invasion of inflammatory cells and necrosis, degeneration and regeneration of muscle fiber by a neuromuscular pathologist.
RESULTS
FSAT T1 CE could objectively describe the severity of involvement in inflammatory myopathies. The quadriceps muscle group, especially the vastus muscle tended to be most severely and frequently involved in inflammatory myositis with FSAT T1 CE (statistically insignificant). The vastus intermedius muscle was more severely involved in dermatomyositis than polymyositis. The signal intensity of abnormal muscle sampled by biopsy correlated positively with the grade of muscle biopsy.
CONCLUSION
MRI shows promise in identifying pathologic muscle in patients suspected of having one of the inflammatory myopathies. The degree of signal intensity on MRI may reflect the severity of grade in muscle biopsy.

Keyword

Magnetic resonance imaging; Muscle; Biopsy; Polymyositis; Dermatomyositis

MeSH Terms

Biopsy
Dermatomyositis
Female
Humans
Magnetic Resonance Imaging*
Myositis*
Necrosis
Polymyositis
Quadriceps Muscle
Regeneration
Subcutaneous Fat