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Statin myopathy and EMG changes

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latinman

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Can statin cause fibrillations/dennervation findings on EMG exam? If that is the case, how long after stopping the statin would the findings not be appreciated anymore? Thx!
 

RUOkie

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Can statin cause fibrillations/dennervation findings on EMG exam? If that is the case, how long after stopping the statin would the findings not be appreciated anymore? Thx!

Yes they can. If the CPK was high enough, you will see typical myopathic findings (membrane instability, low amplitude/polyphasic MUAP, early/fast recruitment).

The duration of effect depends upon severity. However, even in severe cases like we saw with Baychol/Gemfibrozil combo, the EMG findings normalized in 6 months. Those people had CPK's that were >50K
 

Ludicolo

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We don’t get a lot of EMG referrals for “r/o statin myopathy”. Usually, stop the statin – patient gets better – no need for testing.

EMG findings are normal in most statin myopathies, since they preferentially affect type II fibers. As RUOkie states though - a small percentage of patients will get significant muscle necrosis and marked elevation in CPK levels, or even frank rhabdo. In these patients you’ll see proximal fibs, small polyphasics, etc.
 

PMR 4 MSK

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I get some referrals for this, mostly from our rheumatologists. Very rarely, if ever, have I seen anything on needle exam. These mainly serve to rule out other disorders that may be masking as myopathy.
 

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