Clonus: Definition, Causes & Treatment

Clonus: Definition, Causes & Treatment
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  • 0:00 What is Clonus?
  • 0:30 Why Does Clonus Occur?
  • 1:24 How is Clonus Treated?
  • 2:24 Lesson Summary
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Lesson Transcript
Instructor: Danielle Haak

Danielle has a PhD in Natural Resource Sciences and a MSc in Biological Sciences

Clonus is a condition that results in involuntary muscle spasms, most often affecting muscles at the end of the limbs. It may be a condition in and of itself or a symptom of something else.

What Is Clonus?

Clonus is a condition that causes involuntary contractions and relaxing of the muscles, usually in a particular part of the body. It most commonly affects the ankle, knee, upper or lower arm muscles, or the jaw. As you can imagine, these spastic muscle contractions can make walking or moving around difficult, and in serious cases can even cause debilitating fatigue. Think about how much extra work these muscles are doing!

Why Does Clonus Occur?

Clonus is interesting in that it can be a condition in and of itself, or it can be a symptom of another medical condition entirely. Either way, what's happening is caused by a disconnect in information flowing between the central nervous system (the brain and spinal cord) and the affected muscles.

Clonus most often affects muscles at the ends of the limbs; ankles and wrists are most often affected. When clonus occurs as a condition itself, this is usually due to lesions that have formed somewhere on the motor neurons, and contractions may be stimulated by muscle movement.

Other medical conditions that can cause clonus include:

  • multiple sclerosis
  • Huntington disease
  • spinal cord or brain injuries
  • meningitis
  • stroke
  • cerebral palsy

If a person starts experiencing clonus, they should seek medical treatment to find out the cause. Knowing the cause helps in assessing the most effective treatment.

How Is Clonus Treated?

There are a few different treatment methods that have shown to be effective at treating clonus. For milder cases, applying cold treatment to the affected area can help. Cooling the muscles can help limit the neuron activity in the area causing contractions. In other scenarios, oral medications like immune suppressants, anti-convulsants, and tranquilizers can help. Sometimes, injecting botox or phenol into the affected muscle also helps quell the muscle spasms.

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