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Wait, why did my leg just twitch?

Sitting at your desk, a muscle in your leg palpitates quickly. Or a muscle under your eye flutters. These sudden twitches, known as fasciculation, occur commonly and seem random.

But are these spasms simply minor annoyances? Or are they signs of something more. 

“[A fasciculation] is small and it involves one muscle and it is a local problem,” explains Dr. Jagan Pillai, a neurologist for the Center for Brain Health at Cleveland Clinic.

Fasciculation occurs when a muscle spontaneously becomes excited because of nerve miscommunication. Motor neurons, which live in the spinal cord and base of the brain, send their axons out to tell muscles how to move, but in some situations a disruption occurs, causing fasciculation. Exhaustion, anxiety or depression, nicotine, or too much caffeine can make nerves hyper-excited, disrupting the motor neurons and causing a muscle to flutter wildly.

“Fasciculation is a twitching in the muscles because of abnormal firing of the nerves,” says Dr. Kourosh Rezania, an assistant professor of neurology at the University of Chicago Medical Center.

 “Very often it’s of unclear significance and doesn’t lead to any long term problems.”

Because physicians believe things such as stress and exhaustion cause fasciculation, most solutions are at-home remedies.  

“If [muscle twitches] are really bothersome, the best thing to do is lifestyle modification; get plenty of sleep, exercise, relaxation, and minimize caffeine [consumption],” says Dr. Carlayne Jackson, a professor of neurology at the University of Texas Health Science Center, San Antonio and a member of the American Academy of Neurology.

While the majority of muscle twitches are harmless, fasciculation can be a symptom of other disorders, ranging from very serious to mild. Fasciculation occurring with muscle weakness and atrophy can be a sign ALS, also known as Lou Gehrig’s disease. 

“If [patients] have fasciculation and no weakness, it is unlikely it will have an ominous outcome,” explains Jackson.  

Having frequent fasciculation does not mean that one will develop ALS or any other disease. People with ALS complain more of muscle weakness and pain, Rezania says. 

A less serious, rare condition—known as cramp fasciculation syndrome—causes cramps, pain, fasciculation, and fatigue.

“Cramp fasciculation symptom does not become ALS,” stresses Rezania. “The nerves are excitable and that causes increased symptoms.”

Pillai notes that if patients complain of jerks in their body, doctors must determine the cause of fasciculation—twitches can also be related to diseases such as MS, epilepsy, thyroid disease, or kidney disease, but these disorders almost always have other symptoms associated with them. And physicians must diagnosis whether the movements are fasciculation or myoclonus, which are sudden, involuntary muscle twitches, impacting a group of muscles. Hiccups and hypnic jerks are both forms of myoclonus.  

“[Fasciculation] is commonly noted in normal people, but it could be a sign of a neurological problem. If it is persisting for a long time, it should be taken more seriously than [a twitch] that lasts for a few minutes or an hour,” Pillai says.

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