Résumé :
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Background –Muscle histopathology may be inconclusive because of the patchy muscle involvement in inflammatory myopathies. Imaging techniques may be of use in selecting the exact site for biopsy. Objective – To evaluate the role of muscle Magnetic resonance imaging, ultrasound in site selection for muscle biopsy in inflammatory myopathies, and to compare it with the conventional site for muscle biopsy. Material and methods – Patients with Inflammatory Myopathy from our neuromuscular clinic, were randomized for muscle biopsy to be done according to site selected by MRI or Ultrasound of the muscles of the thigh or from conventional site (right vastus lateralis muscle). All patients underwent MRI and USG and a skin marker indicated the site selected for biopsy. The muscle biopsy was performed according to the randomized group by a blinded investigator. Results – 29 patients with the diagnosis of IM were randomized for muscle biopsy into the MRI group (10 patients) USG group (10 patients) and conventional group (9 patients). Mean age of patients was 36.52 +/- 14.46 yrs. Clinical diagnosis was dermatomyositis in 8(27.6%) and polymyositis in 21 (72.4%) patients. Patients in the MRI group had a conclusive diagnosis in 100% cases, in the USG group in 90% cases and conventional group in 78% cases. Biopsy was inconclusive or normal in 3 patients –in the conventional or USG arm. Repeat biopsy in these patients, on the basis of MRI findings were suggestive of IM. The difference in the results of either arms were not statistically significant. Conclusion – MRI of the muscles is a sensitive test to select the exact site for muscle biopsy in patients with Inflammatory myopathies, superior to USG and conventional methods to select the site for muscle biopsy. Larger studies are required to further substantiate this finding.
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