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 mind for most people is that of a person suffering from seizures, sudden and violent contractions throughout the body that make him shake in a bed. hospital or on the ground.

Indeed, seizures are one of the most visible and important symptoms of epilepsy (in fact, their diagnosis is made, among other aspects, 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 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 in a sudden, rhythmic, repetitive and totally involuntary way, with violent contractions of one or more muscle groups.

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 types can be established depending on the area or areas of the brain 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  well- defined regions of the brain. 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 may even serve as a warning of the arrival of future generalized crises. It is also common for a focal crisis to become generalized, activating some brain areas first and expanding to the rest of the brain later, these crises being called secondary generalized.

1.2. Generalized seizures

Generalized seizures are those in which the whole or a large part of the brain is, 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 muscle group torsion and injury are common.

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

2. According to the level of muscle contraction

Another classification could be made based on the level of intensity 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 or 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. According to the cause of the seizures

Seizures can be caused 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 the episode is relapsed in the first twenty-four hours (in which case they can also be called cluster or atypical seizures).

3.3. Organ failure 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 somatoforms cause the subject to suffer them. These types of seizures have the peculiarity that they usually occur only in the presence of others and no longer generate alterations in an electroencephalogram (although these 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 seizures appear.

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