Involuntary contraction or twitching of muscles.
Small muscle movements which appear as trembling skin.
Uncontrollable, localized contraction of a single muscle group that is visible through the skin.
The twitching of an isolated muscle, which may or may not be related to a neuromuscular disorder.
Brief spontaneous contraction of a few muscle fibers, which is seen as a flicker of movement under the skin. It is most often associated with disease of the motor neurons in the spinal cord or of the nerve fibers.
Fasciculation involves unpredictable, inconsistent, and generally ongoing contractions of a muscle that appears to be at rest. Unlike the contractions seen in fibrillation, these fasciculations can be observed through the skin.
Minor fasciculation, like the type that often occurs in the eyelids, is a common phenomenon and usually not a cause for worry. However, if fasciculation persists and is accompanied by muscle weakness, it signifies potential damage to the nerve cells in the spine that regulate the muscle, or the nerve fibers linking the spinal nerves to the muscle. Motor neuron disease is an example of a disorder associated with such symptoms.