What is Clonus: Causes, Diagnosis, Treatment, Outlook

Clonus is a neurological condition that occurs due to damage to the nerve cells and muscles. It leads to involuntary muscle spasms and contractions. The spasms in the clonus occur in a rhythmic pattern.⁽¹⁾ The symptoms are known to be common in extremities, especially the wrist, knee, and ankle, and also in calves and biceps. Clonus can also occur in the jaw. The damaged nerves cause the involuntary contraction of the muscles leading to pain and tightness. This can make everyday activities difficult and can prove to be debilitating.

Clonus occurs when the nerve signals to the brain are disrupted due to any chronic condition. There are a number of chronic conditions associated with clonus, which include:

• Stroke: During a stroke, a part of the brain gets starved of oxygen due to a blood clot. This results in the disruption of nerve signals in the brain.
• Multiple Sclerosis: It is an autoimmune condition that attacks the protective sheath around the nerves and this disrupts the nerve signals to the brain.
• Infection: There are infections such as meningitis and encephalitis that on getting severe cause damage to the brain cells or nerves.
• Major Injuries: Injury to the head may cause damage to the nerves of the brain and spinal cord.
• Serotonin Syndrome: This is a potential reaction that occurs when excessive serotonin builds up in the body. The reason for excessive serotonin build-up could be drug abuse or taking high doses of medication.
• Brain Tumor: A tumor may push the motor neurons in the brain or may cause these areas to swell causing clonus.

Other causes of Clonus include:

• Kidney or liver failure
• Anoxic brain injury
• Lou Gehrig’s disease
• Cerebral palsy
• Drug overdose
• Hereditary spastic paraparesis

Diagnosis of clonus involves a physical examination done by a doctor and inquiry about the details of the complaint such as the area affected the most and the type and intensity of pain in that area.

If the muscle contraction occurs in the doctor’s office, the doctor can examine how fast and how frequent they are contracting.

A few tests may be ordered by the doctors to confirm the diagnosis. These tests include:

• MRI scan to look for damage to the cells and nerves
• Blood test for identifying markers for various conditions
• A spinal fluid test is done to check for spinal cord injury or damage
• A balance test is done to look for coordination issues

A test is performed by the doctor, during which the person is asked to flex his foot in a way the toes are pointing upward and to hold the muscles there. This may lead to continuous pulsing in the ankle. A series of pulses might indicate clonus. However, doctors cannot rely just on this test to diagnose clonus.

What treatment to follow depends on the cause of the condition. There are different treatment methods found and the doctor looks for the one that would suit the best.

There are sedative medications and muscle relaxers that can be helpful in reducing the symptoms of clonus. These medications may cause drowsiness and a person should not drive a vehicle or work on heavy machinery. Other side effects of these medications include mental confusion, lightheadedness, or difficulty in walking.

Any side effects noted should be brought to the doctor’s notice.

Physical therapy may be helpful in improving the range of motion of the damaged area.

Ankle and wrist splints are recommended by the therapist as they can be helpful in improving stability and reducing the risk of accidents.

Botox injections can be helpful to some people with clonus.⁽²⁾ In botox therapy, specific toxins are given to paralyze the muscles of the affected area. As the effect of the injection wears off, a repeat injection may be required.

Surgery is the last option for clonus. In surgery, the part of the nerve responsible for causing abnormal movement is removed.

Heat packs or taking warm baths can help in relieving pain and cold packs help in relieving spasms.

Magnesium supplements and a magnesium bath may help in calming the muscles. But, before starting magnesium consult a doctor as its consumption may alter the action of other medications.

Outlook for clonus depends on its cause. If the injury is the cause the symptoms go away over time and such people may respond well to physical therapy.

If chronic meningitis or multiple sclerosis is causing clonus, long-term treatment may be needed for the management of symptoms.

Sometimes, symptoms of clonus may worsen with the worsening of the condition. In such cases, the doctor and the physical therapist need to work in coordination to provide maximum support to the patient.