Types of seizures: why do they occur and what causes them?

We analyze the different ways in which this neurological symptom can occur.

When we think of neurological disorders such as epilepsy, the first image that comes to most people's minds is that of a person suffering from seizures, sudden and violent contractions all over the body that make them shake in a hospital bed or on the floor.

Indeed, seizures are one of the most common seizures are one of the most visible and important symptoms of epilepsy (in fact, their diagnosis (in fact their diagnosis is made among other things if the subject has had several seizures). But not all seizures are the same, nor do they occur only in epilepsy. In this article we will visualize the different types of seizures.

Seizure: brief definition of the term

Seizures are understood as those spasmodic movements of the voluntary skeletal musculature that occur abruptly, rhythmically, repetitively and totally involuntarily, with violent contractions of one or more Muscle groups.

The convulsions are a symptom of the existence of a cerebral problem that can have diverse origins.. They are usually of short duration (generally up to two minutes), although longer episodes can be dangerous and are treated as an emergency. Their main cause is found in the existence of electrochemical imbalances in the brain, or a hyperexcitability of specific neuronal groups.

Types of seizures

As indicated above, not all seizures are the same, but different types can be established according to the brain area(s) affected, the level of muscle contraction or the causes of the seizure.

1. Classification according to the affected brain areas

Depending on whether the seizures are due to the alteration in a specific brain area or at a general levelDepending on whether the seizures are due to an alteration in a specific brain area or at a general level, we can consider the existence of two main groups of seizures.

1.1 Focal onset seizures or partial seizures

These are seizures due to the alteration of one or several well-determined regions of the brain. The affected area will determine the type of symptoms that will be experienced. The seizure at motor level occurs in a specific part of the body, or even in a hemibody (i.e. in one of the sides of the body).

They can be simple and complex, depending on whether there are alterations of consciousness (the latter being the complex ones). There may be sensory disturbances and perseveration of actions and gestures.and can even serve as a warning of the arrival of future generalized crises. It is also frequent that a focal seizure becomes generalized, activating first some cerebral areas and expanding to the rest of the brain later, being these seizures called secondary generalized seizures.

1.2. Generalized seizures

Generalized seizures are those in which the whole or a large part of the brain is involved, with electrical disturbances appearing in both hemispheres. They usually cause loss of consciousness and appear tonic-clonic seizures. They occur abruptly, although they may be preceded by an aura, and cause the patient to fall. Loss of sphincter control, tongue biting and even twisting and injury to muscle groups are common. and injuries of muscle groups.

This subgroup includes absence seizures (in which there may be mild contractions), myoclonic seizures, tonic-clonic seizures (these being the most representative) or even atonic seizures in which there is no seizure but only loss of muscle tone after a contraction.

2. According to the level of muscular contraction

Another classification could be made according to the level of intensity or the characteristics of the seizure itself. These include the following.

2.1. Tonic seizures

This is a type of seizure in which there is a powerful muscular contraction of one of the muscles or one or more muscle groups. There is a high level of stiffness in the affected muscle or muscles.

2.2. Clonic seizures

Clonic seizures are those that occur repetitively every two or three seconds, of short intensity and power.

2.3. Myoclonic seizures

Like clonic seizures, these are small muscle spasms of minimal duration, but which result in involuntary movement of a part of the body.

2.4. Tonic-clonic seizures

Tonic-clonic seizures are the most prototypical seizure types, with both tonic and clonic seizures occurring at the same time. It is the type of seizure that is part of the grand mal seizure.

2.5. Atonic seizures

In this type of seizure there are no real seizures, but the sudden disappearance of muscle tone. Sometimes this disappearance is preceded by a powerful muscle spasm.

3. According to the cause of the seizures

The convulsions can be produced by very different causes. It is important not to identify seizure with epilepsy because, although they are very frequent in this disorder, seizures may also occur with other conditions. Some types are the following.

3.1. Epileptic seizures

Epilepsy is one of the main disorders that appear linked to the presence of seizures.

3.2. Febrile and infectious seizures

The presence of fevers higher than 39 degrees can provoke convulsive episodes without previous neurological alterations to explain them. They can be simple if they are not repeated and last less than fifteen minutes, or complex if there is recurrence of the episode in the first twenty-four hours (in which case they can also be called cluster or atypical seizures).

3.3. Seizures due to organic insufficiencies

The presence of alterations in liver or kidneys can also generate the beginning of convulsive episodes.

3.4. Substance use seizures

Both some medications and certain drugs can cause seizures, both as a side effect and during overdose, or during withdrawal syndromes.

3.5. Hysterical seizures

Seizures do not only arise from medical causes. Certain psychological disorders such as somatoform disorders cause the subject to suffer from them. These types of seizures have the peculiarity that they usually occur only in the presence of others and do not generate alterations in an electroencephalogram (although they are not fictitious symptoms, but psychologically generated).

3.6. Seizures due to anxiety

In some situations of very high anxiety it is possible that motor and somatic alterations arise, being possible that convulsions appear.