What causes spontaneous muscle twitches?

What causes spontaneous muscle twitches?

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Sometimes a small region of my body starts shaking, without any reason and then stops abruptly. Apparently this is a common phenomenon (source: NIH). I researched its cause for a bit and came to know that it is because of nerve excitation.

Why do those nerves get spontaneously excited in the first place, without any conscious, voluntary, internal stimulus being presented?

Short answer
Spontaneous muscle twitches are thought to be caused by spontaneous activation of motoneurons controlling the muscles.

Spontaneous muscle activity (twitching) is referred to as muscle fasciculations. Most commonly, they are benign, but they can be associated with certain pathologies too, such as ALS.

Fasciculations are thought to originate due to spontaneous activation of muscle fibers due to processes in the motoneurons. At the axonal endings there are synapses that junction onto the muscle. The axonal tips of motoneurons are thought to be highly sensitive to depolarization (electrical firing), which is what triggers acetylcholine release and muscle contraction. The complicated process itself takes a small fraction of a second. If any of this happens involuntarily, then the muscle fiber contracts spontaneously (source: ALS Association).

Specifically, it is thought that spontaneous depolarization of motoneurons are the cause of fasciculations. This decreased firing threshold can be the cause of disease, disrupted ion homeostasis in the body, fatigue, drugs and other causes (Blum & Rutkove, 2007).

Note that spontaneous / random activity in neurons is not only possible, it is quite common. Especially in neurons close to firing threshold, such as the motoneurons responsible for muscle activity, slight perturbations in ion concentrations inside or outside the cell can trigger an action potential. Further, channel opening is a stochastic process, meaning that even voltage-gated Na+ channels can open without a depolarization being present; although the chance is slim that will happen, it can statistically still happen. Stochastic processes like this can cause neurons to fire spontaneously, without a stimulus being present.

- Blum & Rutkove, The Clinical Neurophysiology Primer, Springer (2007)

Causes of muscle twitches and how to relieve them

Experiencing a muscle twitch can be uncomfortable and irritating. But what causes a muscle twitch, and could it indicate an underlying health condition?

A muscle twitch is an involuntary contraction of the fibers that make up a muscle.

Nerves control muscle fibers. When something stimulates or damages a nerve, it causes the muscle fibers to contract, resulting in a twitch. A person can often see or feel these twitches below the skin.

In this article, we explore the numerous causes of muscle twitches. Most of the reasons for them are harmless though some are more serious. We also discuss how to treat and prevent muscle twitches.

Muscle twitching, also known as fasciculation, has many common causes. These include:


Strain or overuse of a muscle can cause twitches.

When a person exercises vigorously or for a long period, they may experience muscle twitching.

Research suggests this muscle twitching may happen after exercise for two reasons:

  • Firstly, exercise can lead to muscle fatigue. Muscle fatigue triggers twitching and cramping in overworked muscle fibers.
  • Secondly, exercise may cause an electrolyte imbalance through sweating. Electrolytes play a role in muscle contraction. An electrolyte loss within muscle fibers may trigger twitching.

The arms and legs are common places to experience muscle twitching that overexertion causes. The most worked muscles are most likely to twitch, which can include the calf, thigh, or biceps, depending on the exercise.

Not getting enough sleep

Brain chemicals, or neurotransmitters, play a role in transmitting information from the brain to the nerves that control muscle contraction.

Sleep deprivation may affect how neurotransmitter receptors work. This means excess neurotransmitters may build up in the brain.

The impact that a lack of sleep has on neurotransmitters function may lead to muscle twitching.

A common place to experience muscle twitching from tiredness is in the eyelid.


Drinking too much coffee, tea, or energy drinks that contain caffeine may cause muscle twitching.

Caffeine is a stimulant. When a person has too much of it, caffeine can stimulate muscle twitching anywhere in the body.

Calcium deficiency

The body needs calcium to support proper muscle function. Having a calcium deficiency may cause muscle twitching. Calcium deficiency is known as hypocalcemia.

People can get calcium from dairy products, soya beans, tofu, nuts, and leafy greens.

Magnesium deficiency

Magnesium also plays a role in keeping the nerves and muscles healthy. Magnesium helps to transport calcium across cell membranes to support nerve and muscle function.

Having a magnesium deficiency may cause muscle twitching anywhere in the body, including the face. Magnesium deficiency is known as hypomagnesemia.

Causes of magnesium deficiency include:

If people do not address a magnesium deficiency, it may increase their risk of cardiovascular disease.

Vitamin D deficiency

Nerves need vitamin D to carry messages to and from the brain to the body’s muscles. Having a vitamin D deficiency may cause muscle weakness and twitching.

Causes of vitamin D deficiency include lack of exposure to sunshine and poor diet.


Muscle mass is up to 75 percent water. Water also helps to carry nutrients and minerals to muscles to support their function.

When a person does not drink enough water, they may develop dehydration. Having dehydration may cause muscle twitching.

Stress and anxiety

Experiencing psychological stress or high anxiety levels may prompt excess muscle tension. This complication can lead to muscles twitching.

Muscle twitches caused by stress can occur anywhere in the body.

Certain medications

Certain medications can lead to involuntary muscle twitching. This reaction may be a side effect or due to interactions with other drugs.

People can discuss side effects and drug interactions with the doctor when taking a new medication.

Muscle twitching that is not explained by one of the common causes above may indicate an underlying health condition.

Health conditions that can lead to muscle twitching include:

Pinched spinal nerve

A pinched spinal nerve, known as radiculopathy, may cause muscle twitching and spasms. Other symptoms include a tingling or numb feeling in the foot or leg.

A herniated disk can cause a pinched nerve, often the result of trauma. When a disk in the spine is damaged, it may squeeze the root of the corresponding nerve.

Amyotrophic lateral sclerosis

ALS is a rare neurological condition.

Muscle twitching may be a sign of a degenerative neurological condition called amyotrophic lateral sclerosis (ALS). This is a rare condition.

ALS causes a person’s nerve cell function to deteriorate gradually.

Nerve cells, or neurons, control a person’s voluntary muscle function, which allows people to move. When a person’s neurons stop functioning, their muscles are not able to work properly. This causes:

Over time, a person with ALS may lose the ability to control their movements. This can make walking, talking, eating, and breathing difficult.

Isaacs’ syndrome

Isaacs’ syndrome is a neuromuscular condition that may cause muscle twitches.

A person with Issacs’ syndrome has overactive peripheral nerve axons. This means that their nerves continuously trigger their muscle fibers. This causes muscle contractions even when someone is resting.

Other symptoms of Isaacs’ syndrome include:


Muscle twitching may be a sign of lupus, though this condition is not common.

Lupus is a long-term autoimmune condition where a person’s body mistakenly attacks healthy tissue.

Lupus may cause certain muscle groups to become inflamed. This inflammation is called myositis. Muscle twitching is a symptom of myositis.

Multiple sclerosis

Rarely, muscle twitching may be a sign of multiple sclerosis (MS). MS is a degenerative condition that affects a person’s central nervous symptom.

A common symptom of MS is spasticity. Spasticity is when muscles become stiff and contract involuntarily. Muscle twitching may be a sign of spasticity.

Other symptoms of MS include:

  • fatigue
  • numbness or tingling
  • weakness
  • dizziness
  • reduced sexual function
  • chronic pain
  • changes in cognition
  • walking difficulty
  • vision problems

A muscle twitch and a muscle spasm are both involuntary contractions of a muscle, although they are not quite the same.

A muscle twitch is a short contraction that may happen repeatedly. It can cause discomfort but is not typically painful.

A muscle spasm is a prolonged contraction that may cause pain. Muscle spasms are also known as muscle cramps. They often happen after exercise.

The doctor may ask a person to discuss when their muscle twitching started, how often it happens, and how it feels. They may also ask about related symptoms.

If the doctor thinks a person’s muscle twitching is due to an underlying condition, they will give the individual a series of tests. This may include electromyography to assess muscle and nerve function.

A balanced and varied diet can provide essential vitamins and minerals for muscle health.

The common causes of muscle twitching are easy to treat and prevent at home through lifestyle changes to keep the nerves and muscles healthy and functioning well. These lifestyle changes include:

  • eating a more healthful, balanced diet
  • taking dietary supplements to address deficiencies
  • exercising moderately, with proper warmups and cooldowns
  • reducing caffeine intake
  • getting plenty of sleep
  • avoiding or managing stress with yoga, mindfulness, or meditation
  • staying hydrated

If an underlying health condition is the reason for a person’s muscle twitches, the doctor will work with the individual on a treatment plan.

If someone experiences muscle twitching that one of the common causes above cannot easily explain, they should speak to their doctor.

It is also a good idea to speak to the doctor if muscle twitching occurs alongside other, new symptoms.

Muscle twitching has many everyday causes that are not serious. People can easily treat these causes at home and prevent them through specific lifestyle changes.

Some causes of muscle twitching are more serious, but these conditions are mostly rare. The health conditions that may cause muscle twitching are explored above.

If a doctor diagnoses someone with a degenerative condition, such as MS or ALS, they will support them to manage their symptoms. While these conditions have no cure, the right treatment plan can ensure a person maintains a good quality of life.

Treatment Treatment

There is limited information in the medical literature about the treatment of cramp-fasciculation syndrome (CFS). Much of what is available describes individual cases. Some people with CFS improve without treatment. Treatment with carbamazepine, gabapentin, lamotrigine, or pregabalin (medications that reduce the hyper-excitability of nerves) was described as helpful in improving symptoms in individual cases. Immunosuppressive therapy (e.g., prednisone ) has been used to treat cases of CFS that did not respond to other treatments. [3]

Decisions regarding treatment should be carefully considered and discussed with a knowledgeable healthcare provider.

What causes spontaneous muscle twitches? - Biology

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“Twitching of various muscles are, in medical lingo, termed fasciculations, which are small, local, involuntary contractions of muscles in any location (usually outside the butt) that may be visible under the skin,” explains Morton Tavel, MD, Clinical Professor Emeritus of Medicine, Indiana University School of Medicine, and author of “Health Tips, Myths and Tricks: A Physician’s Advice.”

Common sights for fasciculations are the eyelid, a finger or toe, the arch of the foot, the calf and the front and back of the thigh.

But the butt, though not among the most common locations for twitching, can definitely develop this.

The three main muscles of the buttocks are the gluteus maximus, gluteus medius and gluteus minimus: the “glutes.”

Causes of Twitching Muscles butt

Dr. Tavel explains, “They arise as a result of spontaneous depolarization [de-charging] of nerve cells causing synchronous contraction of muscle fibers within a single group of these cells.

“Although fasciculations have a variety of causes, the majority are benign.

“They are encountered by virtually all healthy people, though for most, they are quite infrequent. In some cases, however, their presence can be rather annoying.”

The top reasons for a twitching muscle are exercise (particularly strenuous or prolonged), anxiety and mineral deficiency.

If your butt has been twitching lately, ask yourself if you recently did any glute-engaging exercise.

More than once, the muscles in my butt were twitching away after I went on a long grueling hike.

The twitching wasn’t noticeable until I settled into a comfortable chair later on that day and began working on my computer. I then felt the fasciculations.

And the truth is, I LOVED them! They felt like the fingers of a deep tissue massager. I enjoyed this built-in massage!

Pathological Cause disease

Dr. Tavel says, “Unusually, they can also be due to disease of the nerve cells, in which case they are persistent and associated with other, more widespread muscular disorders.”

If your only symptom is the twitching in your butt (the type of twitching that you’ve very likely experienced many times with an eyelid), and especially if your rump muscles have very recently carried you through a Zumba class, running, strength training or yoga …

… then you should just relax, empty the fearful thoughts from your head and sleep like a baby.

“If a neurological examination and other tests are otherwise normal, a diagnosis of benign fasciculation syndrome is usually made, and it is best ignored,” says Dr. Tavel.

What Are the Common Tic Disorders?

The majority of tics are not severe. So they have very little effect on a person's quality of life. In some instances, though, tics may occur often enough to be disruptive and troubling. When they do, they can affect many areas of a person's life, including school, work, and social life.


Doctors use four characteristics to identify and diagnose tic disorders:

  • the age when tics began
  • duration of the tics
  • severity of the tics
  • whether tics are motor or vocal or both

Transient tic disorder. This disorder most commonly appears in youth. It affects up to 20% of school-age children. Transient tic disorder is characterized by the presence of one or more tics for at least one month but less than one year. The majority of tics seen in this disorder are motor tics, though vocal tics may also be present.

Many children with the disorder experience multiple episodes of the transient tics, which may vary in how they manifest over time.

Chronic motor or vocal tic disorder. While transient tics disappear within a year, chronic tics can last for a year or more. Chronic tic disorder is characterized by the presence of one or more long-lasting tics. They may be either motor or vocal, but not both. For a diagnosis of chronic tic disorder, symptoms must begin before age 18.


Chronic tics occur in less than 5 in 100 children.

Tourette's syndrome. In some instances, what appears to be a chronic tic may be a sign of Tourette's syndrome. This syndrome is the most severe tic disorder. It is characterized by the presence of both motor tics and vocal tics.

Since many people with the disorder have not been diagnosed, it is unknown exactly how many people in the U.S. are living with Tourette's syndrome. Experts estimate that 138,000 children in the U.S. have the condition. Symptoms typically begin when children are between ages 5 and 18 years.

The severity of Tourette's syndrome often changes over time. There may be periods of reduced tic frequency followed by heightened tic activity. Fortunately, many people with Tourette's syndrome find that their condition improves as they get older.

When muscles twitch uncontrollably (very slightly) what is happening?

So called fasciculations. Basically, wrong signals are sent down singular nerve fibers (or singular nerve fibers are stimulated for different reasons) to small muscle bundles (so called muscle fascicles), leading to them being excited, contract and twitch a little without a motoric effect (fascicles need to contract in masses within a muscle in order to move a body part). This can either be completely benign in healthy adults (causes are commonly stress related) or sign of different pathologies ranging from electrolyte imbalance (neurons become more excitable, basically this includes magnesium deficiency, potassium, sodium and calcium imbalances among others) to certain neurodegenerative disorders like ALS and diabetic neuropathy where the neurons innervating the muscle (the alpha motoneurons) are degenerated and malfunctioning (muscles don't receive neuron signals in sufficient quantities and become palsy, what ends up arriving at the muscle is expressed as weak movement (if at all) and fasciculation). If you experience fasciculations, it's more likely to be benign (caused by stress, maybe supported by a bit of magnesium deficiency) than related to pathology, but of course if your medical history is suspicious or you feel other debilitating symptoms, go consult a GP/family doctor.

EDIT: little interjection provided by /u/MortRouge:

"Very important about ALS: Fasciculations are NOT a sign that you have ALS, fasciculations in ALS start at a later stage - you would already have noticed not being able to move before that starts."

so yes, really. for some causes like electrolyte imbalance it can be a fairly unspecific early sign, but neurodegenerative diseases typically don't express fasciculations as a first symptom. It really is most likely to be benign and stress related. I won't get any deeper than this though because I might border the medical advice rule accidentally.

EDIT2: Glad people like my post, but please stop asking for medical advice (or other topical questions involving your personal medical situation) here! Apart from it being generally banned from askscience, this is really not the appropriate medium. A proper medical examination would involve checking prior medical history, thorough interviewing, clinical tests, paraclinical tests (including lab and imaging), reviewing, actual diagnosis and appropriate therapy prescription from a certified specialized medical professional who needs to see you in person to make an adequate assessment of your medical situation, none of which I or other r/askscience users, even if qualified, can provide. This is especially true for a symptom so unspecific as fasciculations.

EDIT 3: I noticed it's a little bit troublesome for some people to visualize the magnitude of fasciculations. Here are 2 handy videos that should be helpful: 1 | 2

Symptoms of Dystonia

Generalized involuntary muscle contractions/spasms:
Begin usually in child age and there will often be others in the family, who have had similar symptoms. It often starts with muscles in the feet and legs contracting in spasms pulling toes, the foot or the ankle into wrong position and it will therefore soon be difficult to walk. Within a few years dystonia spread to muscles in the rest of the body resulting in abnormal body positions. There will often be involuntary wringing movement, which prevents the person from walking or sitting upright.

  • Idiopathic generalized dystonia: Slowly progressing involuntary wringing movements of all 4 limbs or possibly the whole body. Begins typically around 5-15 years of age. It is often hereditary.
  • Dopa-responsive dystonia (Segawa): Rare hereditary disorder that begins around 3-4 years of age with involuntary muscle contractions in the legs, particularly when the patient is tired, later spreading to the rest of the body. A substance called L-dopa, can eliminate the symptoms if administered daily in small doses.

Localized involuntary muscle movements:
The symptoms of localized dystonia are limited to individual muscle groups. The most common forms of localized dystonia are torticollis (painful neck spasms), and scoliosis (abnormal curvature of the spine). Typically, symptoms begin in early adulthood. The symptoms depend on what muscle groups are involved. Many also have pain in the involuntarily contracting muscles, as well as in adjacent muscle groups and distorted body position as for example the neck. - There are the following types:

  • Torticollis: Painful spasms and twitching in the neck muscles pulling the head to one side and possibly also leaning a little.
  • Blepharospasm: Involuntary contractions of the muscle around the eyes on both sides. Both eyes are squeezed together so hard that the patient might be unable to open the eyes voluntarily.
  • Hemifaciale spasm: Involuntary contractions of facial muscles on one side only.
  • Cranial dystonia (Meiges syndrome or Bruegels disease): Usually begins at the age 30-70 years with blepharospasm and strange involuntary movements of the face, jaw, tongue, palate, throat, neck and breathing muscles. This leads to grimace and outbreaks of sounds.
  • Writing spasms (or profession convulsions): Some people, who are accustomed to writing, get sudden spasm of the fingers when trying to write. Spasms may also arise in connection with other activities as for example tooth brushing, use of tools or the like. The condition is often painful. The cause is unknown.
  • Medicine induced dystonia: This comes in two forms: Acute occurring alongside the beginning of treatment with neuroleptics (used to treat psychiatric disorders) and after many years of treatment with neuroleptics (Tardive dystonia). Acute medicine induced dystonia occurs after days to weeks of therapy and shows as involuntary forced upward movement of the eyes or squint (cross eye). There may also be dramatic tension and stiffness in the neck and shoulder muscles and a tendency to poke the tongue out of the mouth. The tardive dystonia usually begins in the neck or facial muscles. Some cases fall into the category bucco-mastico-lingvalt syndrome (BML), which means repeated involuntary jaw, tongue and chewing movements. The condition might spread to the entire body if the treatment with neuroleptics is not stopped.

What Is the Calf Muscle?

If there’s one muscle you’re likely familiar with, it’s the calf muscle. If you reach around and grab your calf and flex it, the muscle you are actually feeling just under the surface is called the gastrocnemius muscle in medical terminology.

The top of the muscle attaches behind the knee, and the bottom connects to the Achilles tendon, which stretches all the way down to the heel. If you’re a runner or even just exercise regularly, you probably spend time stretching the calf muscle—one, because it feels really good, and two, because it helps protect the muscle from damage. And who hasn’t woken up in the middle of the night at least once with the dreaded calf muscle cramp?

What is causing that twitching in your muscles?

Ever sit in a chair and feel twitching in your eye? Or maybe your calf muscle. You may suffer from benign fasciculation syndrome.

Dr. Jerry Fleishman of Medstar Franklin Square Medical Center talks about how to manage the condition.

What is benign fasciculation syndrome?

It is a neurological disorder characterized by fasciculations, or twitching of various voluntary muscles in the body.

What are the symptoms of the syndrome?

Since many times this is a chronic disorder, it may lead to a variety of other signs and symptoms that might include generalized fatigue, muscle pain, exercise intolerance, or paresthesias, which is the prickly, burning, pins and needles, tingling feeling. The disorder also can cause muscle spasms, cramping, muscle stiffness, myoclonic jerks (a sudden, involuntary muscle spasm), itching or shakiness in the muscles. Additionally, symptoms may include those of anxiety such as globus, which is the sensation of having something stuck in the back of the throat. Headaches or shortness of breath also have been associated with this condition.

The symptoms may last for months or even years. In some cases, symptoms may linger or may come and go with periods of remission, while other times the symptoms may be prominent. In some instances, remission periods may become longer over time with symptomatic episodes occurring less and less.

The symptoms and severity differ from person-to-person.

What causes the twitching, numbness or tingling that people with the condition have?

By definition, BFS is idiopathic, which means that there is no known cause. There are certain medications that may trigger fasciculations but do not cause BFS. These may include Dramamine, Benadryl, Sudafed, Nortriptyline, Ritalin, or beta agonists of which the latter are a class of medications that are commonly used to relax the muscles of the airways and result in easier breathing in those people whom may have a history of asthma, bronchitis or emphysema, for example.

Fasciculations also may be due to trauma or an injury or may be symptoms of anxiety or depression. Some studies have suggested that there is a link to other stress-related conditions such as irritable bowel syndrome, heartburn and headaches. There are also some people who lack certain minerals, including magnesium or calcium, who also may develop fasciculations or even muscle cramps. Fasciculations also have been linked to strenuous exercise, alcohol, cigarette smoking, fatigue, excessive caffeine intake or in the setting of an underlying sleep disorder.

What body part is the twitching more likely to occur?

Twitching most often occurs in the calves and thighs but can occur almost anywhere in the body. Fasciculations or twitching of muscles may appear randomly or may persist in one muscle for an extended period of time. Fasciculations will be most noticeable when the body is at rest. There may be associated pain in the affected muscle.

The disorder is often confused with ALS, or Lou Gehrig’s disease. What is the different between the two diseases and how do you determine which one it is?

It is a distinctly different disorder from ALS. A major symptom of ALS is muscle wasting when muscles atrophy or become smaller over time. The person with ALS will begin to feel weaker as the condition progresses. People with ALS are many times not aware of their fasciculations and see their physician because of increasing weakness and reduced mobility that limit normal daily activities.