A muscle twitch can have many meanings, such as twitching to fall asleep, twitching of the eyelids, myoclonia (muscle twitching with a movement effect), tic (regular or irregularly recurring contractions), spasms (involuntary, painful muscle contractions), tremor (shaking), or fasciculations.
What all muscle twitches have in common is that they are involuntary contractions (twitches) of the muscles.
For tremor, see “Tremor” below; for spasm and spasms, see “Cramps and spasms of the musculature” below.
In the following, we will focus on the topic of fasciculations.
Fasciculations (ICD-10-GM R25.3: Fasciculation) are irregular and involuntary contractions of muscle fiber bundles, which become noticeable by visible muscle twitches when they develop in superficial muscle layers.
Fasciculations are not a specific sign of the presence of disease; they are classified as benign. Only the presence of other symptoms characteristic of a disease usually gives reason to clarify the fasciculations.
Fasciculations can be a symptom of many diseases (see under “Differential diagnoses”).
In one study, healthy volunteers showed fasciculations on ultrasound in 43% of cases, occurring mainly in the abductor hallucis longus muscle (elongated, thin skeletal muscle on the medial side of the foot that is part of the foot musculature). Muscle groups above the knee showed only occasional fasciculations.
Course and prognosis: Fasciculations often appear on the face or extremities and usually have no clinical value. Only the presence of further symptoms makes it necessary to clarify them. In such cases, a neurologist should most likely be consulted, since pathologic (pathological) fasciculations usually have a neurologic cause.Typical triggers of benign (benign) fasciculations are stress, ingestion of stimulants (psychoactive substances; stimulants), or disorders of electrolyte metabolism (e.g., hypocalcemia (calcium deficiency), hypokalemia (potassium deficiency), and hypomagnesemia (magnesium deficiency)).
