Investigations and Diagnosis
Tissue biopsy is the gold standard. Macroscopically this reveals pale muscle tissue. Microscopically infarcted patches of myocytes. Necrotic muscle fibers are swollen and eosinophilic and lack striations and nuclei. Small-vessel walls are thickened and hyalinized, with luminal narrowing or complete occlusion. Biopsy cultures for bacteria, fungi, acid-fast bacilli and stains are negative in simple myonecrosis.
Creatine kinase is found to be normal. ESR is elevated. Planar X-ray reveals soft tissue swelling and bone scan shows non specific uptake. CT shows muscle oedema with preserved tissue planes (non-contrast enhancing). MRI shows increased signal on T2 weighted images within areas of muscle oedema. Arteriography reveals large and medium vessel arteriosclerosis occasionally with dye within the area of tissue infarction . Electromyography shows non specific focal changes.
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