What are the findings of electromyography (EMG) and nerve conduction studies (NCSs) indicative of acute corticosteroid-induced myopathy, and how can ultrasonography be used in the diagnosis of myopathy?

Updated: Sep 10, 2019
  • Author: Patrick M Foye, MD; Chief Editor: Stephen Kishner, MD, MHA  more...
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Some case reports have indicated abnormal EMG findings, including abnormal spontaneous activity (positive sharp waves and fibrillation potentials), early recruitment, and small, polyphasic motor units. There have also been findings suggestive of the development of associated neuropathy following high-dose corticosteroid treatment. [21, 22]

Ultrasonography can be used to visualize details such as muscle echogenicity, muscle size, and the presence or absence of muscle movement. The thickness and overall appearance of the intermuscular/intramuscular fascia can also be assessed using ultrasonography. Myopathic disorders often display ultrasonographic abnormalities, which can vary between different types of myopathies. [6]

Using ultrasonography, Minetto et al found echo intensity and thickness of the lower limb muscles to be significantly greater in patients with active Cushing disease than in those with remitted disease. Thus, in patients with steroid-induced myopathy, ultrasonography may help with diagnosis of the condition and assessment of disease progression. [23]

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