Myokymia describes successive, involuntary, small muscle contractions or tics that affect a bundle of muscles. The muscle movements are usually visible under the skin and can be felt. Each contraction lasts for less than one second. Myokymia can affect any muscle group and can cause digits and eyelids to move. It can also cause stiffness in hands. Myokymia is not affected by position or movement.
Myokymia is similar to "fasciculations" which are irregular, flickering, twitching movements that are also caused by involuntary contractions of muscle bundles. Fasciculations are finer than myokymia and appear more as rippling movements of the muscles. The difference between the two is really a medical definition and is best detected by EMG.
Other forms of involuntary muscle movements are cramps which are painful contractions of skeletal muscles and myotonia which is more persistent than both myokymia and fasciculations.
Myokymia, especially that of the eyelid, is usually a self-resolving and benign condition. However, myokymia is seen in a number of serious nervous conditions including multiple sclerosis.
In MS, myokymia in facial muscles (hemifacial spasms) is particularly common although it can occur in any muscle groups. Myokymia tends to come and go and is often particularly troublesome when the person is hot or fatigued.
Treatments for myokymia include drugs like Dilantin, Tegretol, Neurontin and Botulinum Toxin but many people simply live with the condition.
In MS, myokymia is caused by the spontaneous discharge of demyelinated axons (axons are the long extensions of nerve cells (neurons) that carry nervous transmissions).
Fasciculations, cramps, twitches, myokymia
Understanding Multiple Sclerosis