What are the findings of electromyography (EMG) and nerve conduction studies (NCSs) indicative of chronic (classic) corticosteroid-induced myopathy?

Updated: Sep 10, 2019
  • Author: Patrick M Foye, MD; Chief Editor: Stephen Kishner, MD, MHA  more...
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Answer

Motor and sensory NCS results typically are normal. Repetitive stimulation studies do not reveal significant decrement or increment. EMG studies reveal normal insertional activity with little abnormal spontaneous activity (positive sharp waves and fibrillation potentials). EMG may reveal a mild decrease in motor unit action-potential amplitude during maximal recruitment. In moderate-to-severe cases, studies may show an early recruitment pattern. [17]


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