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What is a Clonus Test?

A clonus test is carried out to diagnose a series of involuntary muscle contractions that may indicate the presence of neurological conditions. Let us go into the details and know about clonus test in this HealthHearty article.
HealthHearty Staff
Last Updated: Feb 22, 2018
Have you ever felt your muscle twitching for a few seconds or so? Then, just as they occurred suddenly, they disappear on their own? There are many reasons as to why our muscles twitch involuntary. In some cases, it may indicate a serious neurological condition. In order to detect these underlying neurological conditions, one is asked to undergo a clonus test. So, what is clonus test and how is it conducted? Before we go into the details of the test, it is important to understand what is clonus.

What is Clonus?

The repetitive, rhythmic contraction and relaxation of muscles is called clonus. There are different types of clonus like wrist clonus, ankle clonus, and kneecap clonus. Among these, the most common form is the ankle clonus. They occur due to abnormalities in the neuromuscular activities. When muscles are stretched, it leads to deep tendon reflex. This causes clonus, and it is often confused as symptoms of myoclonus. However, myoclonus is defined as the uncontrollable jerks of a muscle, or a group of muscles. You must be wondering how does involuntary muscle twitching affect a person. Well, when you cannot control the movement of the muscles, it causes problems while walking, leading to change in gait, or holding things steadily in your hands. In some cases, clonus becomes so severe that it leads to pain.

What Causes Clonus?

Clonus causes includes a variety of neurological problems and disorders. Clonus test helps us determine these underlying problems. Many times, neurological conditions occur due to upper motor neuron lesions. These nerves originate from the cerebral cortex and carry electrical impulses sent by the brain. When these nerves are damaged, clonus occurs.

One of the main causes of nerve damage is spinal injury. Sometimes, hepatic encephalopathy, stroke, and multiple sclerosis can also lead to clonus. When the tightening of the spinal cord occurs due to disc diseases, it leads to ankle clonus. Disorders like spastic paraparesis, Huntington's disease, epilepsy, Creutzfeldt-Jakob disease, meningitis are also known to cause clonus. Serotonin syndrome, which is an adverse reaction to drugs like serotonergic, or other drugs like cocaine, LSD, oxycodone can also lead to clonus.

Clonus Test

As you can see, there are a number of neurological disorders and diseases causing clonus. In order to be sure about the presence of some problem within the muscles, it is important to carry out clonus test. This is a simple test where the doctor either carries out ankle clonus test or wrist clonus test. Let us know briefly about an ankle clonus test.

The test is carried out by performing a rapid dorsiflexion of the foot. The foot is held in slight tension in the dorsiflexed position. Dorsiflexion is the position that occurs after the foot is bent backwards gently. After the foot is released, a reaction occurs. The foot comes back to its normal position on begin when released, indicating absence of clonus. However, if the foot repeats the motion of going backward and forward involuntarily, it indicates presence of cerebral palsy or neurological disorder. If there are five beats or more, it indicates the presence of clonus.

Do not take severe clonus lightly. Clonus causes a lot of problems like unsteady gait while walking. Therefore, a person is given walking aides like crutches, walking sticks, etc., to walk. Surgery is carried out on the spine as clonus treatment, and in most cases physical therapy proves helpful in relieving the condition.

This was all about clonus test. As you can see, it is a simple test performed by neurologists to find five beats or more of ankle clonus to carry out further diagnosis of the condition.
Hand holding painful ankle