What are fasciculations?

Fasciculations are involuntary movements of individual muscle fibers (muscle twitches) that are visible under the skin but do not result in any movement of the entire muscle. They are not specific to ALS but are a common symptom that can occur in various conditions—including benign ones—as well as in healthy individuals.

In ALS, fasciculations usually occur throughout the entire body and with high intensity. Fasciculations are particularly common in the early stages of ALS. In rare cases, fasciculations are noticed before the onset of myatrophy and paresis. The presence of fasciculations in isolation, without concurrent evidence of paresis and myatrophy, does not justify suspicion of ALS.

Overall, fasciculations are a common phenomenon that is predominantly nonspecific and frequently occurs in the general population (“benign fasciculations”). Furthermore, they can occur in connection with specific neurological disorders (“pathological fasciculations”). This dual meaning of fasciculations often leads to frequent, mostly unfounded concerns about ALS. Fasciculations that persist for several months and are not accompanied by other neurological symptoms (muscle wasting, paralysis, hyperreflexia, or spasticity) make the presence of ALS highly unlikely.