Is an EMG Ever Wrong?

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entszelizavetth

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I know this topic has been beaten to death but if like to know, are emg's ever wrong? Can it miss als? I rember reading this on als forums but I don't visit those anymore... So if you have a clean emg, can you rule out als 100%?
 
There is no definite answer, unfortunately. As a neuropathologist, I can tell you:1) Once the process of neurodegeneration is in place, EMG will not miss it (when done properly in the affected muscles) - the active and chronic denervation is quite obvious together with ongoing reinervation.2) Before the degeneration of anterior horn cells, there is a hyperexcitability phase in which case the EMG can be clean (except for fasciculations). But as the latest studies from this year mentions, this phase is "seldom longer than a few months".Anyway, in 99% cases, EMG done after 6-12 months can be considered as pretty safe.
 
Then why do most people on here say clean EMG equals no ALS? It's so confusing that's where the fear comes from… So as doctor after how many months of twitching would you feel confident saying it is not ALS if the EMG is still normal?
 
People here say it because for majority of cases it is true. I am a neuropathologist, I do not work with living patients but generally as I mentioned, 6 months is considered as enough by most ALS specialists. But that does not mean you have to wait 6 months, clean EMG is a solid evidence that nothing bad is going on. But to be absolutely sure, the follow up is usually recommended.
 
Yes, pretty much - 99,9% as nothing is 100% ;) Be it ALS, in 6 months period one would expect at least slight changes in motor unit pattern or F-wave abnormalities (persistence <50%, high amplitude...)No problem, I am glad I could help ;)
 

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