Generalized tonic-clonic seizure: its symptoms and characteristics

Among all the seizures that a person can suffer 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.

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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 most associated with the prototypical image of epileptic seizure, and is usually associated with metabolic dysregulations in the organism of the sufferer.

It is normally 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 seizures without being accompanied by other varieties.


There are several symptoms that the person can suffer before, during and after suffering from generalized tonic-clonic seizures.

Although most seizures appear without giving sudden and sudden warning , some people may suffer a prodrome. He warns that something is not going well in his body, and that he will suffer an epileptic crisis. Normally, the prodrome manifests itself in the form of premonitory feelings that predict that a crisis will be suffered.

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

1. Tonic phase

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

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

The skeletal muscles tense , causing the limbs to remain stiff and the patient falls to the ground because they cannot stand.

The eyes turn blank or stop directing towards 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 expulsion of air violently from the lungs. This is known as ictal scream.

The skin turns blue, because breathing has lost its rhythmicity and there is a lack 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 eye pupil to expand (mydriasis).

One of the risks during the tonic phase is that the tongue is bitten, since the jaw is very tightly clenched. It can also bite your cheek and cause a large oral lesion.

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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 is giving way to muscle relaxation . Lasts longer than the tonic phase, lasting about a minute.

The relaxation is not complete, since the muscles immediately tighten again and then relax , causing the seizures themselves.

The person shakes violently, being at this stage the moment in which you can injure against objects that are in the room. You can also go 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 their blood circulation altered , in addition to altering the 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, starts to cry and vomits.

Possible causes

Although epilepsy has been thoroughly studied, 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 an explanation of why they appear.

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

It has been hypothesized that certain deregulations at the level of neurotransmitters and chemicals present in the central nervous system would be behind the onset of this type of seizures. 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 (flickers and flashes), high estrogen levels and antihistamines.

Throughout the history of psychiatry, with the use of electroconvulsive treatments for different types of psychological disorders, they have been able to replicate in laboratory conditions and, also, apparently therapeutic generalized tonic-clonic seizures.

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


The diagnosis can be made through the use of neuroimaging techniques , especially with electroencephalography (EEG). However, it should be said that for the diagnosis by this tool to be reliable it is necessary to record the brain activity while it is taking place 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 electric shocks. On the other hand, short waves occur during the clonic phase. The electroencephalogram is shown with many peaks during the tonic phase, and then passes 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 him should make sure that the person who is suffering from them is in a lying position , in order to avoid that, while losing consciousness, he accidentally introduces saliva into the airways and suffocates.

You must be close to the person to see how the epileptic episode is occurring and calculate how long the crisis is going on. If possible, all objects should be removed from the place to prevent the person from crashing into them. It is not recommended to hold the person while he is convulsing, nor to put objects in his mouth, since the limbs can be contracted, herniated and, if something is put in his mouth, drown with it.

As for treatment, as with other types of seizures, anticonvulsants are prescribed to prevent them . Also, if the brain area involved in the onset of these crises is known, surgery may be performed, in addition to stimulating the vagus nerve.

To avoid the occurrence of 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.


by Abdullah Sam
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