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<embedvideo service="youtube" Alignment="right">https://youtu.be/sLzSRF_gBeU</embedvideo><embedvideo service="youtube" Alignment="right">https://youtu.be/h7O-xa0nq-U</embedvideo>Myokymia refers to involuntary, spontaneous, localized, transient or persistent quivering movements of a muscle. When myokymia involves the extremities, the movements are usually coarser, slower and more prolonged than fasciculations and often have an undulating character. Myokymia involving the face is typically more vermicular. The top video shows myokymia involving the quadriceps muscle in a patient with a denervating process, with simultaneous EMG. The louder, low frequency periodic thumping in the background is a myokymic discharge; the softer, higher frequency discharges are fibrillation potentials. The bottom video shows myokymia of the quadriceps due to rattlesnake envenomation. Myokymia can be difficult to distinguish from fasciculations. Typically, fasciculations dance and flit from spot to spot, myokymia tends to persist in the same location for a more prolonged period.
Myokymia often occurs in normal individuals. Mild, usually fleeting, myokymia is common, especially in the orbicularis oculi, and is of no clinical significance. These movements often worsen with fatigue and with hypercaffeinism. Patients often require reassurance. Myokymia occurs in a variety of disease states; it is thought to arise because of biochemical perturbations in the nerve microenvironment due to demyelination, a toxin (such as rattlesnake venom), or other factors
