Clonus is a type of neurological condition that creates involuntary muscle contractions. This results in uncontrollable, rhythmic, shaking movements. People who experience clonus report repeated contractions that occur rapidly. It’s not the same as an occasional muscle contraction.
Clonus primarily occurs in muscles that control the knees and ankles. It’s usually brought on by excessive stretching of these muscles.
Less commonly, clonus can also affect other areas of the body, such as the:
Read on to learn more about this condition.
The exact cause of clonus is not fully understood. There is usually a problem with the electrical pathway involved in muscle movement. It’s most often seen in conditions that involve muscle spasms.
Conditions that often lead to clonus include:
- amyotrophic lateral sclerosis (ALS), a rare neurological disease that affects muscle control and movements, sometimes known as Lou Gehrig’s disease
- brain injury
- cerebral palsy
- certain metabolic diseases, such as Krabbe disease
- hereditary nerve diseases, like hereditary spastic paraplegia, a group of rare genetic disorders that effect the spinal cord and cause gradual loss of muscle tone and control
- multiple sclerosis (MS)
- serotonin toxicity
- spinal cord injury
In some cases, liver or kidney failure can also lead to clonus due to the buildup of waste products within the body. This waste buildup can affect normal brain function.
Clonus and spasticity
Spasticity often occurs with clonus. It involves long-term muscular tightness.
Spasticity, as seen in clonus, is caused by damaged nerves among the brain, spinal cord, and muscles. This abnormal activity is thought to disrupt muscle movement by causing involuntary contractions, stiffness, and pain.
Other neurological and muscular issues that may occur alongside clonus can include:
- overactive deep tendon reflexes
- fixed joints, known as contractures
- increase in muscle tone, known as hypertonicity
- involuntary leg-crossing, sometimes called scissoring
Clonus and MS
A common condition associated with clonus is multiple sclerosis (MS). This is a disease of the central nervous system that disrupts signals between the brain and the body. MS can cause involuntary muscle movements.
MS is a progressive disease, which means it can get worse over time without treatment. Treating MS can help control muscle spasticity and clonus.
How it’s diagnosed
Clonus is a long-term condition. Before you can be treated for it, your doctor will need to diagnose the condition.
First, your doctor will perform a physical exam. They will look at the areas that have the most contractions and pain. If you have a muscle contraction while at the doctor’s office, your doctor will measure how many “beats” or contractions occur.
Your doctor may order certain tests to diagnose clonus, as well. These tests can also help your doctor identify any undiagnosed conditions you might have. Possibilities include:
- balance and coordination tests
- blood tests
- MRI of the brain
- spinal fluid samples
No single test can diagnose the cause of clonus. You might need to take a series of tests before your doctor makes a diagnosis.
Treating clonus involves a combination of medications and therapies. Talk to your doctor about all of the following options. Clonus treatments can be used on a trial-and-error basis until you and your doctor find what works for you.
Medications, primarily muscle relaxants and sedatives, help reduce clonus symptoms and spasticity. These may include:
- baclofen, a muscle relaxant
- clonazepam (Klonopin), a type of sedative
- diazepam (Valium), a type of sedative
- tizanidine (Zanaflex), a muscle relaxant often prescribed when baclofen doesn’t work
These types of medications can cause sleepiness. You shouldn’t drive a vehicle while taking these drugs.
Other side effects can include:
- difficulties walking
Be sure to talk to your doctor about all the benefits and risks associated with these types of medications.
Botox injections can help some people with clonus. While widely known as a wrinkle treatment, Botox actually works by relaxing major muscle groups. These types of injections need to be administered on a regular basis because their effects wear off over time.
Physical therapy may complement the benefits offered by your medications. A physical therapist may use exercise to promote range of motion while also stretching your muscles. In turn, you will likely see an improvement in your symptoms.
You can also help manage clonus symptoms at home. For example, cold packs can help soothe achy muscles while heat pads can provide pain relief. Stretching exercises may alleviate clonus symptoms. Professionally recommended splints for the wrists and ankles may help certain people, as well.
Your doctor will recommend surgery only as a last resort if medications and physical therapy don’t provide any relief. Surgery for clonus often involves cutting the nerve passageways that cause abnormal muscle movement.
The overall outlook for clonus depends on the underlying cause. In short-term conditions, such as acute injuries or illnesses, clonus and muscle spasms may resolve overtime. Chronic neurological conditions, like MS, rely on long-term treatments to help control symptoms. Sometimes, muscle issues can worsen if your condition progresses. Early intervention is vital for proper treatment and follow-up care.