Clonus is a neurological condition that occurs when nerve cells that control the muscles have become damaged. This damage causes involuntary muscle contractions, or spasms.

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Clonus spasms often occur in a rhythmic pattern. Symptoms are common in a few different muscles, especially in the extremities. These include the ankles, knees, wrists, and jaw, as well as the calves and biceps.

Damaged nerves can cause muscles to misfire, leading to involuntary contractions, muscle tightness, and pain.

Clonus, which health experts sometimes refer to as clonus reflex, can also cause a muscle to pulse for an extended period. This pulsing can lead to muscle fatigue, which may make it difficult for a person to use the muscle later.

Clonus can make everyday activities strenuous and can even be debilitating. In this article, learn more about the causes and treatment.

While researchers do not fully understand the exact cause of clonus, it appears to be due to damaged nerve passageways in the brain.

Experts associate a number of chronic conditions with clonus. As these conditions require specialized treatment, the outcome may vary in each case.

Conditions associated with clonus include the following:

Multiple sclerosis (MS) is an autoimmune disorder that attacks the protective sheath around the nerves. The resulting damage disrupts the nerve signals in the brain.

A stroke starves a part of the brain of oxygen, usually due to a blood clot. A stroke may cause clonus if it damages the area in the brain that controls movement.

Infections, such as meningitis and encephalitis, can damage brain cells or nerves if they become severe.

Major injuries, such as head trauma from a serious accident, may also damage the nerves in the brain or spinal cord.

Serotonin syndrome is a potentially dangerous reaction that occurs if too much serotonin builds up in the body. This buildup could be due to drug abuse, but it may also result from taking high doses of medications or mixing certain medicines.

A brain tumor that pushes against the motor neurons in the brain or causes these areas to swell may lead to clonus.

Other causes of clonus include anything that has the potential to affect the nerves or brain cells, such as:

To diagnose clonus, doctors may first physically examine the area that has become most affected and ask about pain in that area.

If a muscle contracts while a person is in the doctor’s office, they may monitor the contraction to see how fast the muscle is pulsing and how many times it contracts before stopping.

A doctor can also elicit a clonus reflex by tapping on the tendon of the affected joint when it is in a relaxed position.

Testing

To confirm the diagnosis, a doctor will most likely order one or more of the following tests:

  • MRI scans, to check for damage to the cells or nerves
  • blood tests, to help identify markers for various conditions associated with clonus
  • spinal fluid samples, to help check for spinal cord injury or damage
  • balance tests, to help illustrate coordination issues

A physical test may also help doctors diagnose clonus.

During this test, they will ask the person to quickly flex their foot so their toes are pointing upward, and then hold the muscle there.

This may cause a sustained pulsing in the ankle. A series of these pulses may indicate clonus. Doctors do not rely on this test to diagnose clonus, but it can help point them in the right direction during the diagnostic process.

Treatment for clonus will depend on the underlying cause. Doctors may try many different treatment methods before finding the one that works best for each person.

Medications

Sedative medications and muscle relaxers can help reduce clonus symptoms. Doctors often recommend these drugs in the first instance for people with clonus.

Medications that may help with clonus contractions include:

  • baclofen (Lioresal)
  • dantrolene (Dantrium)
  • tizanidine (Zanaflex)
  • gabapentin (Neurotonin)
  • diazepam (Valium)
  • clonazepam (Klonopin)

Sedatives and anti-spasticity medications can cause drowsiness or sleepiness. People taking these medications should not drive a vehicle or operate heavy machinery.

Other side effects may include mental confusion, lightheadedness, or trouble walking. A person should discuss these side effects with a doctor, especially if they are likely to disrupt a person’s work or everyday activities.

Other treatments

Other than medication, treatments that may help reduce clonus include:

Physical therapy

Working with a physical therapist to stretch or exercise the muscles may help increase the range of motion in the damaged area.

Some therapists may recommend wrist or ankle splints for some people, as they can provide structure and improve stability, reducing the risk of accidents.

Botox injections

While there is limited research on the effectiveness of Botox injections, some people with clonus may respond well to them.

Botox therapy involves injecting specific toxins to paralyze muscles in the area. The effects of Botox injections wear off over time, so a person will require repeat injections on a regular basis.

Surgery

Surgery is often the last resort. During a procedure to treat clonus, surgeons will cut away parts of the nerve that are causing abnormal muscle movements, which should relieve symptoms.

While medical treatments for clonus are important, home remedies can be valuable in supporting these efforts.

Using heat packs or taking warm baths may relieve pain, while applying cold packs may help reduce spasms.

Some people may also find that a magnesium supplement or magnesium salt bath helps relax the muscles. However, individuals should consult a doctor before trying magnesium, as it can interact with other medications.

The outlook for clonus may depend on the underlying cause. Where a sudden injury or illness causes clonus and muscle spasms, the symptoms will likely go away over time or respond well to physical therapy.

Chronic conditions, such as MS, meningitis, or a stroke, may require long-term treatments for symptom management.

Clonus may sometimes get worse if the underlying condition progresses. Many people find they can manage symptoms by working closely with a doctor and a physical therapist.