Generalized tonic-clonic seizure: its symptoms and characteristics

Of all the seizures a person can experience during an epileptic seizure, the generalized tonic-clonic seizure is probably the best known in 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 peculiarities, as well as possible causes and treatments.

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Generalized tonic-clonic seizure: what is it?

Generalized tonic-clonic seizure, also called ‘grand mal’ , is a type of epileptic seizure in which both tonic and clonic contractions of the muscles occur. This variety of seizure is the one most associated with the prototypical image of epileptic seizure, and is usually associated with metabolic dysregulations in the organism of the sufferer.

Normally it is believed that people who suffer from epilepsy only suffer from this type of crisis, 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 that the person can suffer before, during and after suffering generalized tonic-clonic seizures.

Although seizures appear suddenly, suddenly, and abruptly in most cases, some people may experience a prodrome. This warns that something is not going well in your body, and that you will have an epileptic crisis. Normally, the prodrome manifests itself in the form of premonitory feelings that predict that a crisis is about to occur.

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

1. Tonic phase

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

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

The skeletal muscles tighten , causing the limbs to stiffen and the patient to fall to the ground because they cannot stand up.

The eyes are rolled or no longer directed at a specific point, 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 violent expulsion of air from the lungs. This is known as an ictal cry.

The skin turns blue, because the breath has lost its rhythmicity and there is a deprivation of oxygen in the body.

The sympathetic system responds forcefully , causing blood pressure to rise, the heart to beat faster, and the pupil to expand (mydriasis).

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

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2. Clone phase

After the tonic phase comes the clonic, 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.

Relaxation is not complete, since the muscles immediately re-tighten and then relax , thus causing the seizures themselves.

The person shakes himself violently, being in this phase the moment in which he can injure himself against objects that are in the room. It can also be rolled lying on the ground.

3. Posttictal phase

Once the tonic and clonic phases have occurred, the posttictal phase comes, in which multiple events can occur.

The patient’s brain can see altered blood circulation , as well as altered levels of neurotransmitters.

The person is totally confused, in addition to suffering amnesia , although progressively he will become aware that he has suffered a crisis.

It is quite likely that the person, after having suffered physically and psychologically during the episode, will cry and vomit.

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 that allows us to explain the reason for their appearance.

However, it has been seen that certain types of epileptic seizures that occur unilaterally at the cerebral level, only involving one of the two hemispheres, can evolve into crises 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 dysregulations at the level of neurotransmitters and chemicals present in the central nervous system are behind the appearance of this type of seizure. Some triggers of this type of crisis, in addition to a certain genetic predisposition to suffer them , are fatigue, malnutrition, sleep deprivation, stress, hypertension, diabetes, rapid light changes (blinks and flashes), high estrogen levels 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 replicable under laboratory conditions and, apparently, also therapeutic.

In the case of people who suffer from symptomatic epilepsy, it has been seen, using neuroimaging techniques, that they present neurons with lesions, causing them to transmit nerve signals inappropriately and, thus, the movements of the crisis occur.


Diagnosis can be made using neuroimaging techniques , especially with electroencephalography (EEG). However, it must be said that for the diagnosis using this tool to be reliable, it is necessary to record brain activity while it occurs 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 fast waves, followed by high-amplitude electric shocks. On the other hand, during the clonic phase short waves occur. The electroencephalogram is shown with many peaks during the tonic phase, before moving on to a more irregular synalepha during the clonic phase.

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When a person suffers from generalized tonic-clonic seizures, the people around them must ensure that the person suffering from them is in a recumbent position , in order to avoid accidentally introducing saliva into the airways while suffocating while losing consciousness.

You must be close to the person to see how the epileptic episode is occurring and calculate how long the crisis is lasting. If possible, all objects should be moved away from the place to prevent the person from colliding with them. It is not recommended to hold the person while he is convulsing or to put objects in his mouth, since it can contract the extremities, herniate and, if something is put in the mouth, choke on it.

As for treatment, as with other types of epileptic seizures, anticonvulsant drugs are prescribed to avoid them . Also, in case the brain area involved in the appearance of these crises is known, surgical intervention can be carried out, in addition to stimulating the vagus nerve.

To avoid 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, high in fat and protein.


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