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

When we think of neurological disorders like epilepsy, the first image that comes to mind for most people is of a person suffering seizures, jerky and violent contractions throughout your body that cause you to shake in a hospital bed or on the floor.

Indeed, seizures are one of the most visible and important symptoms of epilepsy (In fact, its diagnosis is made, among other aspects, if the subject has had several seizures). But not all seizures are the same, nor are they unique to epilepsy. In this article we are going to visualize the different types of seizures.

The seizure: brief definition of the term

Seizures are understood as those jerky movements of the voluntary skeletal muscles that occur from abrupt, rhythmic, repetitive and totally involuntary form, with violent contractions of one or more groups muscular.

Seizures are a symptom of a brain problem that can have various origins. They are usually short-lived (usually up to two minutes), although longer episodes can be dangerous and are treated as an emergency. Its 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 ones can be established. types depending on the brain area or areas 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 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 more brain regions well determined. The affected area will mark the type of symptoms that will be experienced. The seizure at the motor level occurs in a specific part of the body, or even in a half body (that is, on one side of the body).

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

1.2. Generalized seizures

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

Within this subgroup can be found the absence crisis (in which there may be slight contractions), myoclonic, tonic-clonic (these being the most representative) or even atonic ones in which a seizure does not occur but the loss of muscle tone after a contraction.

2. According to the level of muscle contraction

Another classification could be made depending on the intensity level or the characteristics of the seizure itself. Among them, the following stand out.

2.1. Tonic seizures

It is a type of seizure in which there is a powerful muscle contraction of one of the muscles or of 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 repeatedly every two to three seconds, of short intensity and power.

2.3. Myoclonic seizures

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

2.4. Tonic-clonic seizures

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

2.5. Atonic crisis

In this type of crisis, true seizures do not occur, but rather the sudden disappearance of muscle tone. Sometimes this disappearance is preceded by a powerful muscle spasm.

3. Depending on the cause of the seizures

Seizures can be produced by many different causes. It is important not to identify seizures with epilepsy because, although they are very common in this disorder, seizures from other conditions can also appear. Some types are as follows.

3.1. Epileptic seizures

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

3.2. Febrile and infection seizures

The presence of fevers greater than 39 degrees can cause seizures 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 a recurrence of the episode in the first 24 hours (in which case they may also be called cluster seizures or atypical).

3.3. Organ insufficiency seizures

The presence of alterations in the liver or kidneys can also generate the onset of seizures.

3.4. Substance use seizures

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

3.5. Hysterical seizures

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

3.6. Seizures due to anxiety

In some situations of very high anxiety, motor and somatic alterations may arise, and seizures may appear.