What Do Fasciculations or Muscle Twitching Mean?

Q & A with Edward Kasarskis, M.D., Ph.D.

Q: Many people who have muscle twitching worry that they have ALS since it’s often associated with the disease. If a person has muscle twitches a lot, or even daily, could it be the beginning of ALS?

A: Muscle twitching is very common, especially when people have had too much coffee, too much stress, or not enough sleep.  Does this sound familiar?  

Of course, the first thing many people do when they have a symptom is to run to the computer to see what Dr. Google has to say about it.  I just did that and I got 1,390,000 results in 0.25 seconds.  One of the first items that popped up was a Wikipedia definition leading to the term "fasciculations," (which means muscle twitching), suggesting the symptoms could be associated with ALS. And then of course it’s natural to panic.  So if you were not under stress at the start before you went to the Internet, you certainly would be after consulting Dr. Google.

But take a breath.  There are many things that can cause muscle twitching, including fatigue, anxiety, or even a pinched nerve in the spine. Muscle cramps, too, are very common, and can be caused by such things as over-exertion or even dehydration. Just watch any basketball game: it seems there’s always somebody on the floor dealing with a significant leg cramp.

Symptoms such as muscle twitching and muscle cramps don’t tell you much just by themselves; they are very common and non-specific.  To diagnosis ALS, a physician needs to see signs of progressive muscle weakness. 

What causes fasciculations? They originate at the very tips of the nerves, called axons, as they come close to being in contact with the muscle. The tips of the axons are thought to be overly sensitive to depolarizing (electrical firing), which is what triggers a muscle to contract.  When a nerve fires, zillions of times a day upon request, an electrical impulse starts in the nerve, moves out toward the muscle, triggers the release of a chemical (acetylcholine) that "swims" across the gap between the nerve axon and the muscle, and binds to a receptor on the muscle causing it to fire. The complicated process itself takes a small fraction of a second.  If any of this happens involuntarily, then the muscle fiber contracts without your permission and behold, a muscle twitch or fasciculation!

Some people with ALS wonder if the presence of muscle twitching means they have a bad or fast-moving version of the disease. In fact, having fasciculations doesn't correlate with how rapidly the disease progresses.

I would suggest most people with fasciculations or muscle cramps wait a few months although there’s no hard and fast rule -- before seeking a medical evaluation.  Often the twitching or cramping will just stop on its own. If it doesn’t, it makes sense to get your problem evaluated. 

An internist or a neurologist will ask you some questions, learn more about what you’ve been experiencing, and hold your limb in a relaxed position and study the twitching. He or she may then want you to have a muscle test (an EMG) to better understand what could be going on.  Blood tests might be needed as well.

Often, the results will look normal but the doctor may suggest waiting a little longer to see if anything further develops over the next few months.  Even in the 21st century, there is sometimes no instant test or procedure that can give you a clear answer about a problem. With fasciculations, this is certainly the case. 

Waiting is a challenge for most people, but the odds are heavily in your favor that you don't have ALS.  As they say, "common things are common," and ALS is not common, especially when compared to excessive caffeine use and stress. 


Dr. Kasarskis
Dr. Kasarskis

Edward Kasarskis, M.D., Ph.D. is Director of the multidisciplinary ALS Center at the University of Kentucky Neuroscience Center in Lexington, Kentucky, professor in the Department of Neurology at the University of Kentucky, and Chief of Neurology at the VA Medical Center in Lexington KY.