Are Muscle Twitches a Symptom of MS?

Physical therapist working on woman's leg

Muscle twitching occurs when nerves misfire, causing groups of muscle fibers to contract. They can occur in healthy people and rarely signal the presence of an underlying disease, especially if they occur without other symptoms.

However, if you have multiple sclerosis (MS) and experience muscle twitches, you might wonder whether they're a symptom of your condition.

The answer to this question is a bit complex, as it depends on exactly what you mean by muscle twitching. Let's take a closer look at fasciculations (not usually related to your MS) and spasticity or clonus (likely related to your MS).

Understanding Fasciculations

Lower motor neurons transmit nerve signals from your spinal cord to your muscles. When these nerve signals are disrupted, muscle weakening and wasting will eventually occur, along with uncontrollable muscle twitching (called fasciculations). 

Fasiculations are a hallmark symptom of diseases that affect the lower motor neurons, like amyotrophic lateral sclerosis, better known as ALS or Lou Gehrig disease.

Other lower motor neuron diseases that may cause fasciculations include post-polio syndrome, spinal muscular atrophy, and progressive muscular atrophy.

Multiple sclerosis very rarely involves the lower motor neurons, which is why fasciculations are usually not a symptom of the disease. However, people with advanced MS sometimes have lower motor neuron involvement, which can lead to muscle twitching—although, again, this is rare.

Besides neurological diseases, fasciculations may also be a symptom of certain diseases and conditions outside the nervous system, such as:

  • An overactive thyroid gland
  • An overactive or underactive parathyroid gland 
  • Electrolyte abnormalities (e.g., low phosphate levels or high calcium levels)
  • Severe kidney disease
  • Nutritional deficiencies, such as vitamin D, vitamin B12, magnesium, and potassium

Understanding Spasticity and Clonus

Spasticity describes muscle tightness and stiffness, as well as spasms that can be constant or sudden (like a twitch, as described by some people).

Spasticity is a common symptom in MS (unlike fasciculations) and often affects one or both of the legs. It results from disrupted signals between the upper motor neurons and the lower motor neurons. In other words, there is impaired nerve transmission from the brain and spinal cord to the nerves that control your muscles.

In addition to muscle spasms and stiffness, clonus may also occur in MS. Clonus describes the repetitive jerking or twitching of muscles. For example, if a doctor taps on the knee of a person with MS to elicit the knee-jerk reflex, that person may demonstrate a brisk reflex or in more severe cases, clonus, in which their knee-jerk reflex is hyperactive (the muscle that controls the knee shakes rhythmically and uncontrollably).

Understanding Benign Muscle Twitching

Putting aside fasciculations, spasticity, and clonus, it's important to understand that a run-of-mill muscle twitch here and there is likely nothing to worry about.

Muscle twitches that are unrelated to an underlying disease or abnormality can be triggered by a number of things, including:

  • Strenuous exercise
  • Tiredness or lack of sleep
  • Too much caffeine or alcohol
  • Exposure to extreme cold
  • Hyperventilation
  • Stress or anxiety
  • Certain medications, such as water pills or steroid medicines

In these instances, muscle twitches are benign and short-lived, meaning they are not a serious health concern, and come and go quickly.

Two uncommon conditions called benign fasciculation syndrome and cramp fasciculation syndrome cause frequent muscle twitches and, in the latter syndrome, muscle cramps.

These conditions are believed to be due to hyperexcitable nerves and are not associated with loss or nerve or muscle function.

A Word From Verywell

It's always disconcerting to develop a new or unexplained symptom when you're living with MS. If you experience frequent or troublesome muscle twitches, be sure to see your doctor. There may be a simple explanation and relatively easy intervention to control this symptom.

If no cause can be identified, at least you'll have the reassurance of knowing it's not something you need to worry about.

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Article Sources
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  • National Institute of Neurological Diseases and Stroke website. (March 2012). Motor Neuron Diseases Fact Sheet.

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