Key result
Qualitative muscle MRI could not distinguish different types of myopathies compared with biopsy and genetic testing, as only 30% of myositis patients showed contrast medium uptake.
Why the study?
The role of muscle magnetic resonance imaging in diagnostic procedures for myopathies remains controversially discussed.
Does qualitative muscle MRI distinguish different types of neuromuscular diagnostic groups in patients with suspected myopathy?
Observational (n=191)
Does qualitative muscle MRI distinguish different types of neuromuscular diagnostic groups in patients with suspected myopathy?
Qualitative muscle MRI findings, including edema and gadolinium enhancement, are insufficient to distinguish between different types of myopathies or secure a diagnosis of myositis.
Qualitative muscle MRI should not guide myopathy diagnosis; leaves open whether quantitative imaging improves differentiation.
Background and aims: The role of muscle magnetic resonance imaging (MRI) in the diagnostic procedures of myopathies is still controversially discussed. The current study was designed to analyze the status of qualitative muscle MRI, electromyography (EMG), and muscle biopsy in different cases of clinically suspected myopathy. Methods: A total of 191 patients (male: n = 112, female: n = 79) with suspected myopathy who all received muscle MRI, EMG, and muscle biopsy for diagnostic reasons were studied, with the same location of biopsy and muscle MRI (either upper or lower extremities or paravertebral muscles). Muscle MRIs were analyzed using standard rating protocols by two different raters independently. Results: Diagnostic findings according to biopsy results and genetic testing were as follow: non-inflammatory myopathy: n = 65, inflammatory myopathy (myositis): n = 51, neurogenic: n = 18, unspecific: n = 23, and normal: n = 34. The majority of patients showed myopathic changes in the EMG. Edema, atrophy, muscle fatty replacement, and contrast medium enhancement (CM uptake) in MRI were observed across all final diagnostic groups. Only 30% of patients from the myositis group ( n = 15) showed CM uptake. Discussion and conclusion: The study provides guidance in the definition of the impact of muscle MRI in suspected myopathy: despite being an important diagnostic tool, qualitative MRI findings could not distinguish different types of neuromuscular diagnostic groups in comparison with the gold standard histopathologic diagnosis and/or genetic testing. The results suggest that neither muscle edema nor gadolinium enhancement are able to secure a diagnosis of myositis. The current results do not support qualitative MRI as aiding in the diagnostic distinction of various myopathies. Quantitative muscle MRI is, however, useful in the diagnostic procedure of a suspected neuromuscular disease, especially with regard to assessing progression of a chronic myopathy by quantification of the degree of atrophy and fatty replacement and in exploring patterns of muscle group involvements in certain genetic myopathies.
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Urban et al. (2021) conducted an observational in suspected myopathy (n=191). Qualitative muscle MRI vs. Muscle biopsy and/or genetic testing was evaluated on Distinction of different types of neuromuscular diagnostic groups. Qualitative muscle MRI could not distinguish different types of myopathies compared with biopsy and genetic testing, as only 30% of myositis patients showed contrast medium uptake.
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