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What are tonic-clonic seizures?

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Tonic-clonic seizures are characterized by the body stiffening and rapid jerking movements. They can impact your health, but there are treatments that can help.
Medically reviewed by Heidi Moawad, M.D.
Updated on

Seizures are when sudden changes in normal movement or behavior occur due to disruption in electrical firing in the brain.

Normally, tiny electrical impulses in our brain travel along neurons throughout the body, typically in a pattern. When this pattern is disrupted, it can cause a seizure. Generally, these are categorized as either generalized seizures, which happen on both sides of the brain, or partial seizures, which start in one area of the brain.

Tonic-clonic seizures can be partial or generalized. They are what most people think of when they imagine an epileptic seizure. They’re characterized by a loss of consciousness and intense muscle spasms.

What are tonic-clonic seizures?

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Tonic-clonic seizures have two rapidly alternating phases:

  • tonic phase: stiffening of the body, often accompanied by loss of consciousness
  • clonic phase: jerking muscle contractions

These phases can happen in any order or switch between one another. Tonic-clonic seizures were previously known as grand mal seizures.

They are considered one of the most dangerous types of seizures because the person often loses consciousness and the ability to control their movements. It’s possible that they might fall and hurt themselves, have difficulty breathing, or lose control of their bladder or bowels. These seizures usually occur in people who have epilepsy.

Although the exact number of people who experience these seizures is unknown, researchers have estimated that 10–20% of people with epilepsy experience frequent tonic-clonic seizures.

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What causes them?

According to the National Institute of Neurological Disorders and Stroke, no cause can be found for about half of people affected by epilepsy.

The electrical disturbance that occurs in the neurons of people who get tonic-clonic seizures is typically due to genetic factors. However, head injuries, stroke, or brain tumors are also known causes, as these can all affect the brain’s function, disrupting the neurons and leading to seizures.

What are the symptoms?

Tonic-clonic seizures may start with a partial seizure (affecting only one side of the brain) or aura. This is sometimes described as a strange feeling, like a warning sign. It might present as abnormal sensations such as vertigo, nausea, or anxiety. You may also experience a change in mood or emotion leading up to the seizure.

In the tonic phase, you will lose consciousness and may fall. Spasms can force air out of your lungs, resulting in a moaning sound. Your chest muscles may contract, making it difficult to breathe. 

In the clonic phase, quick jerking movements may affect the body. This usually lasts about 1 to 3 minutes, after which the body relaxes, and the breathing regulates.

After the tonic-clonic activity, the person may remain unconscious as the brain returns to normal — this is called the postictal period. Awareness is gained gradually, but a host of symptoms may linger, including confusion, muscle soreness, memory loss, or sadness. 

As the brain recovers, depressed or combative emotions and behaviors may be expressed. 

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How are they treated?

A person having a seizure should immediately be put in the recovery position (on their side) to keep airways clear and prevent being deprived of oxygen (asphyxiation) or choking. The area around them should be cleared for their safety. 

Most seizures will stop spontaneously. A seizure that does not stop on its own within a few minutes may require a dose of anti-seizure medication. After a first tonic-clonic seizure, studies have shown that the risk of having another is about 40%.

If you have had a seizure, you should see a doctor and give them as much information as possible from those who were there at the time. They may order tests, such as an MRI scan of the brain to see if there is any identifiable cause or treatable problem, like a brain aneurysm.

Based on this, a healthcare plan should be developed, which may include anti-epileptic drugs (AEDs) to modulate the chemicals in your brain to keep seizures under control. 

Drugs such as carbamazepine (Tegretol) and diazepam (Valium) are anti-epileptic drugs that have been shown to be effective in some cases. However, AEDs can have unwanted side effects, such as fatigue, agitation, headaches, or rashes. 

Vagus nerve stimulation, where a small electrical device is placed under the skin to change the electrical signals in your brain, is another possible treatment. Voice changes, headache, or cough are some of the side effects.

Brain surgery to remove a part of the brain responsible for the seizures may be sought as a more aggressive treatment. However, this is reserved for unique cases and when AEDs do not work.

A crucial aspect of a treatment plan will include education about avoiding common seizure triggers, such as sleeplessness, alcohol, illness, and some medications. 

Education to prevent bodily harm during a seizure is also crucial. You may be advised to avoid swimming or operating heavy machinery like cars. 

There is typically a period of time when people who have experienced a tonic-clonic seizure are restricted from driving, though this depends on the area.

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Tonic-clonic seizures occur due to a burst of electrical energy in the brain that causes abnormal movements. During the tonic stage, the body stiffens, while the clonic stage is characterized by jerking movements. These can occur in any order.

It can be a serious condition, especially if safety precautions are not taken while the seizure is happening. Treatment options depend on the cause and nature of the seizures, though medications or vagus nerve stimulation may be recommended. 

Those with recurrent seizures should make important lifestyle changes to ensure they remain safe and avoid bodily harm during a seizure.

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