What you think is a muscle twitch from MS (myokymia) may actually be just a harmless fasciculation; there’s a way to tell the difference with these two kinds of muscle twitching.

“Fasciculation and myokymia are two separate conditions,” states a report in the Postgraduate Medical Journal (November 1972) 48, 657-661.

These two conditions “can be distinguished by their clinical and electromyographic Features,” continues the report.

“Fasciculations appear clinically as brief twitches seen scattered in an irregular manner over the surface of the muscle and occurring at irregular intervals.”

What does myokymia look like?

“Myokymia is a slower contraction seen over small bands or strips of muscles, occurring in a regular manner which gives an undulating or rippling appearance to the overlying skin.”

EMG Differences

“Electromyographically, fasciculation is characterized by spontaneous high voltage simple single action potentials firing at random, whereas myokymia is characterized by spontaneous bursts of single action potentials occurring rhythmically at lower amplitudes,” says the paper.

“Each burst may consist of one to several individual action potentials, the constant feature being that they occur rhythmically.

“Sometimes the bursts of action potentials may have a tetanic character (Gutman et al., 1969).”

Though a layperson won’t understand just what all that means, it’s clear that the EMG results for a fasciculation are markedly different when compared to those for myokymia.

So when you see the words “muscle twitching” in a symptom list for multiple sclerosis, you now know that this is ambiguous in several ways:

• Does it mean spasm in a limb?

• Does it mean tremors (shaking)?

• Does it mean the same kind of fasciculation that millions of healthy people get every day, such as twitches in a tired eyelid, fatigued leg or even their nose?

• Does it mean myokymia?

• If it’s myokymia, can it occur in the nose?

Lorra Garrick has been covering medical, fitness and cybersecurity topics for many years, having written thousands of articles for print magazines and websites, including as a ghostwriter. She’s also a former ACE-certified personal trainer.  
Source: ncbi.nlm.nih.gov/pmc/articles/PMC2495329/pdf/postmedj00335-0015.pdf