A generalized tonic-clonic seizure makes a person’s whole body twitch, jerk, and become unconscious. “Grand mal seizure” is an older term for this.

These seizures may be dangerous and can cause injury. Previously, doctors called these seizures “grand mal.” This is an outdated term — medical professionals now use the term “tonic-clonic.”

This article will discuss the symptoms, causes, and diagnosis of tonic-clonic seizures.

It will also look at the risk factors, possible lasting effects, and how to help someone having a seizure.

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Epilepsy, a brain condition, commonly causes tonic-clonic seizures. Certain medications, some infections, and several other health conditions may also cause them.

During a generalized tonic-clonic seizure, a person experiences rapid involuntary alternating jerking and stiffening of the body. This can involve the torso, arms, and legs on both sides of the body. The person is unaware of their surroundings and become unresponsive, sometimes losing consciousness.

Tonic-clonic seizures can last just a few seconds or up to several minutes. Prior to a seizure, a person may experience a visual aura, a change in mood, strange tastes or smells, or headaches.

Tonic stage and clonic stage

Tonic-clonic seizures occur in two stages: The tonic stage and the clonic stage.

During the initial tonic stage, a person may:

  • lose consciousness
  • fall if standing or sitting upright
  • experience muscle stiffness

The clonic stage will immediately follow the tonic stage. During the clonic stage, a person may experience:

  • jerky movements in large muscle groups
  • foaming at the mouth or biting the tongue
  • blue skin or lips
  • loss of bowel or bladder control
  • involuntarily shouting or crying out

After the seizure, there is usually a post-ictal phase. The person will regain consciousness.

However, they may fall asleep or remain unconscious for a period. Most people cannot remember the episode and feel groggy and confused for a few hours.

Both genetic and environmental factors can cause an imbalance.

Some genetic factors include:

  • abnormal neuronal connections that happen when the top layer of the brain does not form correctly
  • abnormal gamma-aminobutyric acid receptors that cannot properly monitor neuron activities
  • potassium channel mutations

Environmental factors include:

A doctor will diagnose a person’s tonic-clonic seizure by evaluating their medical history and recollection of the seizure. They will also perform a physical examination and check for signs of a seizure, such as tongue bites.

Additionally, they will ask about environmental factors — high fevers, drug or alcohol use, drug or alcohol withdrawal, stress, and flashing lights — to determine the cause of the seizure.

Having a tonic-clonic seizure does not necessarily mean a person has epilepsy. However, a doctor may think a person’s seizure is the result of epilepsy if:

  • they have had at least two seizures
  • the seizures were at least 24 hours apart
  • there is no evidence to suggest that other factors caused the seizures

If this is the case, the doctor will perform a number of tests. These may include:

Learn more about how doctors diagnose and help people manage epilepsy here.

There are several risk factors that increase a person’s likelihood of having a seizure. These include:

There is also evidence suggesting that not getting enough sleep and exposure to flashing lights, such as emergency vehicle lights, can trigger seizures in people with certain types of epilepsy.

Although people can get epilepsy at any age, it more commonly develops during childhood.


People often have temporary forgetfulness, trouble with speech, or difficulty moving after a seizure. It is also more common for a person to fall and hurt themselves or bite their tongue when having a tonic-clonic seizure than during other types of seizures.

It is important to note that epilepsy itself does not significantly shorten a person’s life expectancy. However, if a person has another health condition, such as a brain tumor, it may influence their life expectancy.

Although rare, it is possible that a person may sustain a life threatening injury during a seizure. Additionally, sometimes a person can have prolonged seizures. Having a long-lasting seizure can stop oxygen from reaching the brain and cause brain damage.

According to the Centers for Disease Control and Prevention (CDC), seizures do not usually require emergency medical attention.

However, it is vital to seek medical attention if a person:

  • has not had a seizure before
  • has difficulty breathing or waking up after the seizure
  • has a seizure that lasts more than 5 minutes
  • has another seizure soon after the first
  • receives an injury during the seizure
  • has a seizure in water
  • is pregnant or has another health condition, such as diabetes or heart disease

If a person is having a tonic-clonic seizure, people around them can help by:

  1. gently helping them to the floor
  2. turning them onto one side to help them breathe
  3. making sure that the area is clear of anything that may cause injury
  4. placing a folded jacket or blanket under the person’s head
  5. removing eyeglasses and loosening neckties
  6. timing the seizure and calling for emergency medical treatment if it lasts longer than 5 minutes

If it is safe to do so, people can check if the person has a medical bracelet or any other emergency information.

It is important to stay with a person having a seizure until it ends. Once it is over, people should make sure that the person is aware of their surroundings. People should check if the person needs any medical attention, and if they do not, help them get home safely.

It is important for a person to contact a doctor if they experience a seizure that results in an injury. They should also seek medical advice if they have more than one seizure within 24 hours.

If a person has experienced their first seizure, they should visit a doctor. The doctor will be able to diagnose any underlying conditions and, if necessary, prescribe treatment.

The following are answers to common questions about seizures.

What are the phases of tonic-clonic seizures?

The phases of tonic-clonic seizures are:

  • Tonic phase: A person will lose consciousness and their muscles will go stiff.
  • Clonic phase: A person experiences involuntary muscle movements, such as shaking, may lose bladder control and may cry out involuntarily.
  • Post-ictal phase: This is the recovery stage. A person may feel confused, nauseous, tired, and weak.

What should I do if I have a seizure and I am home alone?

Once the seizure is over, assess symptoms and decide whether or not to contact a doctor. It is a good idea to tell a loved one what has happened, and if possible, ask them to come to your home. Taking precautions ahead of time can make a potential seizure when home alone much safer.

How can I manage a major seizure disorder?

People with epilepsy can manage their disorder by:

  • using warning devices
  • following the right diet and exercise plan
  • taking medication regularly
  • getting enough sleep
  • avoiding certain risks, such as swimming alone

What is the outlook after tonic-clonic seizures?

Around 40% of people who have a tonic-clonic seizure go on to experience another one. People are more likely to have more than one tonic-clonic seizure in the days after the first one. However, the risk of another seizure decreases. People are less likely to have seizures if they treat their epilepsy with medication.

Can someone die from a tonic-clonic seizure?

Yes, it is possible to die from a tonic-clonic seizure. For example, some people may seriously injure themselves while having a seizure or drown if they have a seizure in water. It is also possible for someone to die from sudden unexpected death in epilepsy (SUDEP). According to the CDC, this happens in about 1 in every 1,000 people with the condition.

Although tonic-clonic seizures can be scary, they do not always require medical attention. Epilepsy, injury, and environmental factors can cause seizures.

Bystanders can follow some basic first-aid tips to help someone who has a seizure. People with epilepsy can also take anti-epileptic medications to prevent future seizures.