Of all the seizures a person can have during an epileptic seizure, the generalized tonic-clonic seizure is probably the best known within popular culture.

Although it is not the only type of seizure that people with epilepsy can suffer, it is the most prototypical, and in this article we will learn more about its particularities, as well as possible causes and treatments.

Widespread tonic-clonic seizure: what is it?

A generalized tonic-clonic seizure, also called a ‘grand mal’ , is a type of epileptic seizure in which both tonic and clonic muscle contractions occur. This type of seizure is most often associated with the prototypical image of an epileptic seizure, and is often associated with metabolic dysregulation in the sufferer’s body.

It is usually believed that people who suffer from epilepsy only have this type of seizure, but the truth is that only 10% of epileptic patients suffer from this type of seizure without being accompanied by other varieties.


There are several symptoms a person may experience before, during, and after generalized tonic-clonic seizures.

Although most seizures appear without warning , suddenly and abruptly, some people may suffer a prodrome. This warns that something is not going right in your body, and that you will have a seizure. Usually, the prodrome manifests itself in the form of premonitory feelings that predict a seizure.

Once the seizures begin, up to three different phases occur during the seizure, which are the tonic phase, the clonic phase and the postictal phase.

1. Tonic phase

Usually, the tonic phase is the first phase when you have this type of seizure.

The first thing that happens is the rapid loss of consciousness , although it does not always occur completely.

The skeletal muscles are tightened , causing the extremities to become rigid and the patient to fall to the floor because he cannot stand up.

The eyes are rolled up or stopped pointing, and the mouth remains open.

This phase lasts only about ten or twenty seconds and despite the loss of consciousness, the person is able to articulate some sounds, mostly due to the expulsion of air violently from the lungs. This is known as ictal scream.

The skin becomes blue, because the breathing has lost its rhythm and there is a deprivation of oxygen in the body.

The sympathetic system responds in a forced manner , causing blood pressure to increase, the heart to beat faster and the pupil of the eye to expand (mydriasis).

One of the risks during the tonic phase is tongue-biting, since the jaw is clenched very tightly. You can also bite your cheek and cause a large mouth injury.

2. Clone phase

After the tonic phase comes the clone, which is a state in which the tension experienced during the previous phase gives way to muscle relaxation . It lasts longer than the tonic phase, lasting about one minute.

The relaxation is not complete, since the muscles immediately re-tension and then relax , thus causing the actual seizures.

The person shakes violently, and at this stage he or she may be injured by objects in the room. He may also be rolled onto the floor.

3. Postictal phase

Once the tonic and clonic phases have occurred, there is the postictal phase, in which multiple events can occur.

The patient’s brain may see its blood circulation altered , in addition to altering the levels of neurotransmitters.

The person is totally confused, as well as suffering from amnesia, although he or she will progressively become aware that he or she has suffered a crisis.

It is quite likely that the person, after having suffered physically and psychologically during the episode, will start crying and vomiting.

Possible causes

Although epilepsy has been studied in depth, it is known that most of the seizures associated with this problem are idiopathic , that is, they appear suddenly without a clear cause to explain why they appear.

However, it has been possible to see that certain types of epileptic seizures that occur unilaterally at a cerebral level, only involving one of the two hemispheres, can evolve into seizures involving both hemispheres, thus giving rise to a tonic-clonic seizure. Thus, we speak of unilateral focal epileptic seizures that evolve to more complex and bilateral seizures.

It has been hypothesized that certain deregulations at the level of neurotransmitters and chemicals present in the central nervous system would be behind the appearance of this type of seizure. Some triggers for this type of seizure, in addition to certain genetic predisposition to suffer them , are fatigue, malnutrition, sleep deprivation, stress, hypertension, diabetes, rapid changes in light (flashes and blinks), high levels of estrogen and antihistamines.

Throughout the history of psychiatry, with the use of electroconvulsive treatments for different types of psychological disorders, generalized tonic-clonic seizures have been replicated under laboratory conditions and also apparently therapeutically.

In the case of people who suffer from symptomatic epilepsy, neuroimaging techniques have shown that present neurons with lesions, causing them to inappropriately transmit nerve signals and thus produce the movements characteristic of the seizure.


The diagnosis can be made using neuroimaging techniques , especially with electroencephalography (EEG). However, it can be said that for the diagnosis by means of this tool to be reliable, it is necessary to record the brain activity while it is occurring or immediately after the tonic phase of the crisis has occurred.

During the tonic phase, there is a progressive increase in low voltage brain activity, with rapid waves, followed by high amplitude electrical discharges. In contrast, during the clonic phase, short waves occur. The electroencephalogram is shown with many peaks during the tonic phase, and then moves to a more irregular synapse during the clonic phase.


When a person is suffering from generalized tonic-clonic seizures, those around him or her must ensure that the person who is having the seizure is in a lying down position , so as to prevent him or her from accidentally introducing saliva into the airways and suffocating while losing consciousness.

Be close to the person to see how the epileptic seizure is occurring and estimate how long the seizure is lasting. If possible, move all objects away from the place to prevent the person from bumping into them. It is not recommended either to hold the person while he or she is convulsing or to put objects in his or her mouth, as this can cause the extremities to contract, to herniate and, if something is put in his or her mouth, to choke on it.

As with other types of epileptic seizures, anticonvulsant drugs are prescribed to prevent them. Also, if the brain area involved in the appearance of these seizures is known, surgery can be performed, in addition to stimulating the vagus nerve.

To avoid the nutritional conditions that contribute to a higher incidence of these crises, the dietary route is chosen, subjecting the person to a ketogenic diet, that is, one that is high in fat and protein.

Bibliographic references:

  • Krumholz, A., Wiebe, S., Gronseth, G., et al. (2007). Practice Parameter: evaluating an apparent unprovoked first seizure in adults (an evidence-based review): report of the Quality Standards Subcommittee of the American Academy of Neurology and the American Epilepsy Society. Neurology, 69(21). 1996-2007.
  • Schachter S. C. (2009). Seizure disorders. Med Clin North Am. 93(2), 342-351