An Overview of Muscle Twitches

Muscle twitching occurs when nerves misfire, causing groups of muscle fibers to contract. This is common to multiple sclerosis (MS), due to nerve fiber damage that affects signaling between your nerves and muscles.

But there are other possible causes of the various types of muscle twitching too, from fatigue and nutrient deficiency to thyroid disease and more. Some are benign, but others require medical attention.

If you have MS, your muscle twitching may be due to your disease. Or it could be owed to one of these other causes that you may not realize you're living with as well. It's important to sort out the why behind what you're experiencing.

Likewise, for those who have not been diagnosed with MS, it's best not to ignore this symptom, as you may have a condition that requires treatment. There are three types of muscle twitching, each of which has some level of uniqueness to them.

Spasticity

Spasticity describes muscle tightness and stiffness, as well as spasms that can be constant or sudden; some people describe these as a twitch.

Spasticity is a common symptom in MS 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.

Other conditions that may cause spasticity include:

• Adrenoleukodystrophy (ALD)
• Amyotrophic lateral sclerosis (ALS, Lou Gehrig's disease)
• Brain damage
• Cerebral palsy
• Encephalitis
• Meningitis
• Phenylketonuria (PKU disease)
• Spinal cord injury
• Stroke
• Traumatic brain injury

Clonus

Clonus describes the repetitive jerking or twitching of muscles and, like spasticity, is thought to be caused by the faulty nerve transmission characteristic of MS. For example, the normal ankle jerk reflex is instead hyperactive and the muscle that controls the ankle shakes rhythmically and uncontrollably.

In more severe cases, the knee-jerk reflex is hyperactive and the muscle that controls the knee shakes rhythmically and uncontrollably.

Other causes of clonus include:

• Amyotrophic lateral sclerosis (ALS)
• Brain tumor
• Cerebral palsy
• Hereditary spastic paraparesis
• Infections, such as meningitis or encephalitis
• Kidney failure
• Liver failure
• Major injuries to the nerves in the brain or spinal cord
• Stroke

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. 

Fasciculations are a hallmark symptom of diseases that affect the lower motor neurons, like ALS. Other lower motor neuron diseases that may cause fasciculations include post-polio syndrome, spinal muscular atrophy (SMA), and progressive muscular atrophy.

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

Benign Muscle Twitching

It's important to understand that a run-of-mill muscle twitch here and there is likely nothing to worry about. Twitching can occur in healthy people and rarely signals the presence of an underlying disease, especially if it occurs without other symptoms.

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

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

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

Diagnosis

Every disease and condition has its own set of established or widely accepted criteria for diagnosis.

To determine the underlying cause of your muscle twitching, your healthcare provider will likely do a physical examination and ask you questions such as:

• When your muscles began twitching
• Where the twitches occur
• How often the twitches occur
• How long the twitches last
• If you're having any other symptoms

If the healthcare provider suspects your muscle twitching may be due to an underlying condition, they may order blood tests, a magnetic resonance imaging (MRI) scan, a computed tomography (CT) scan, or electromyography to assess the health of your muscles and the nerve cells that control them.

Treatment

Treating the underlying cause of muscle twitches is the primary concern, and it may stop the twitching. What that entails, of course, depends on what condition is at the root of the symptom.

Generally, speaking, medications that may be used to specifically address spasticity and clonus include:

• Neuromuscular blockers
• Muscle relaxants
• Benzodiazepines