Types of Seizures


 What kinds of epilepsy are there?


Epilepsy is more properly known as “the epilepsies”, as there are dozens of different seizure disorders and syndromes in the International Classification. Most basically, however, epilepsy is classified into either Generalized or Partial seizures. In people younger than age 40, about 50% of new cases of epilepsy are generalized seizures, and 50% are partial.


 What are Partial Seizures?reddot

Partial seizures begin in one place in the brain, called the seizure focus, and affect only part of the brain. Depending on where they start and which parts of the brain they involve, partial seizures may or may not alter consciousness or awareness.

 

 

 

 

 

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 What are Generalized Seizures?pulsing

In generalized seizures, abnormal excessive electricity occurs throughout the whole brain at once, with no apparent focal point of onset or warning beforehand. Generalized seizures alter consciousness. They can be convulsive or non-convulsive.

 

 

 

 

 

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 What are Simple Partial Seizures?

Partial seizures that do not alter consciousness are called “simple partial seizures”. They used to be known as “focal” seizures because they occur in only a small part of the brain (the focus). The person having the seizure is aware of what is happening. A simple partial seizure usually lasts only a short time. This type of seizure is also known as an “aura” because it often serves as a warning that a bigger seizure will follow.

Simple partial seizures vary widely from person to person, depending on where in their brain an individual’s seizure focus is located. These seizures consist of an unusual emotion, sensation, or movement.

crossbrainFor example, if the abnormal electrical burst occurs in a specific part of the brain responsible for vision, the simple partial seizure will consist of seeing flashing lights. If it is on the brain’s sensory strip, the person will experience a tingling arm or leg; on the motor strip, their limb will jerk. Some people experience an overwhelming emotion like fear or dread from yet another part of their brain, or smell an unpleasant odour.


 What are Complex Partial Seizures?

Complex partial seizures involve deep, central structures of the brain controlling consciousness, so awareness is altered or lost. These used to be known aspsychomotor or temporal lobe seizures, because they commonly occur in the brain’s temporal or frontal lobes. The brain functions located in these lobes are as complex as the seizures beginning there.

A complex partial seizure may begin as a simple partial seizure (like a funny feeling or emotion) before it spreads to areas of the brain controlling awareness, or it may begin without warning with an alteration in consciousness. With this loss of awareness, the person having a complex partial seizure typically stares blankly, and performs automatic, unconsciously repeated movements, such as lip smacking, picking at one’s clothes, and wandering around, aimless and confused. These movements are called automatisms. During the seizure, the person’s ability to speak, understand and respond is usually affected.

This is a very common type of seizure, although the general public does often not recognize it as epilepsy. People having a complex partial seizure are sometimes treated as if they are drunk or high on drugs, and are often mishandled.


 What is an aura?

An aura is another name for a simple partial seizure. It often serves as a warning that a bigger seizure will follow.


 What are Generalized Tonic Clonic or Grand Mal Seizures?

This is the type of convulsive seizure that most people recognize as epilepsy. It used to be called a grand mal seizure, but now is more properly termed tonic clonic: tonic meaning stiffening and clonic meaning jerking. It is a generalized seizure–meaning most of the nerve cells of the brain are firing at the same time– so consciousness is lost. The person remains unconscious throughout the seizure.

This seizure begins with the tonic phase, in which the body’s muscles stiffen. The person will typically let out a cry, which is really the sound of air being forced out through their contracted vocal cords. The stiffening of the body’s muscles causes the person to fall to the ground. The back arches, the eyes roll back and the limbs extend. Breathing is difficult because of the stiffened chest muscles, and, with the change in available oxygen, the skin colour turns bluish /grey.

Quickly the clonic phase begins, and the limbs, body and head begin to jerk rhythmically. Saliva builds up in the mouth and the tongue may be bitten. Control of the bladder or bowels may be lost. The person continues convulsing, usually for 1-3 minutes, before the jerking slows and the seizure ends. Often a sigh is emitted as normal breathing begins.

After a tonic clonic seizure, the body is limp. The nerve cells in the brain are reacting to their massive misfiring during the seizure. The person is usually confused, sleepy, headachy and irritable for a period of minutes or hours afterwards, and should be allowed to rest until they have fully recovered.


 What are Absence or Petit Mal Seizures?

Occurring most often in children, absence seizures (formerly called petit mal) are very brief staring spells. During this generalized (whole brain) type of seizure, the child loses awareness for a few seconds and becomes unresponsive.

These staring spells begin and end abruptly, usually lasting less than 10 seconds. The child appears “glazed”, “spaced out” or “blank.” Sometimes the eyes roll back during the seizure, and the eyelids flutter briefly. Movements of the mouth, hands and head may also accompany the staring, especially if the seizure lasts more than 10 seconds. Afterward, the child is immediately back to normal alertness and usually unaware that a seizure has occurred.

Absence seizures are often overlooked, or mistaken for daydreaming. A child may have many such seizures over the course of a day, causing frequent interruptions in the continuity of their experience.

The brain produces a characteristic electrical discharge during an absence seizure: the 3-per-second spike-and-wave discharge that shows up on the EEG test, especially when provoked by hyperventilation (or rapid breathing). In approximately 75% of children, absence seizures do not continue after age 18.


 What are Atypical Absence Seizures?

Atypical absence seizures are similar to typical absence seizures [see question above], but usually have more pronounced jerking or automatic movements, a duration of longer than 20 seconds, incomplete loss of awareness, and are associated with other types of seizures and a damaged nervous system. Atypical absence seizures are more likely to occur in children who are developmentally delayed.


 What are Myoclonic Seizures?

The name myoclonic comes from a combination of two terms: myo meaning muscle and clonic meaning jerk. An abnormal discharge of electrical activity in the muscle control area of the brain causes these seizures, which consist of asudden, shocking jerk of the muscles in the arms, legs, neck and/ or trunk. Myoclonic seizures usually involve both sides of the body at the same time, and the person may fall over. Myoclonic seizures occur in a variety of epileptic syndromes, such as juvenile myoclonic epilepsy syndrome.

All myoclonic jerks are not seizures-they can come from the spinal cord, not just from the brain. In fact, it is normal for people without epilepsy to experience a jerk of the body while falling asleep and be startled awake. This is called sleep myoclonus and is not a seizure.


 What are Atonic Seizures?

When a person has a seizure in that part of the brain responsible for muscle tone, their neck, arms, legs or trunk muscles suddenly go limp without warning. The head drops, the arms lose their grip, the legs lose strength or they fall to the ground. This is called an atonic seizure: “a” meaning non and “tonic” meaning stiff. Atonic seizures last just a few seconds. Because they involve such sudden drops without warning, these seizures-known as “drop attacks” –are especially dangerous. People with atonic seizures may have to wear a helmet to protect their heads from injury.


 What are Secondarily Generalized Seizures?

Secondarily generalized seizures begin as partial seizures. They start in part of the brain as an aura (a simple partial seizure) or as a change in awareness (a complex partial seizure) before spreading throughout the brain to become a generalized, usually tonic clonic, seizure, in which consciousness is lost. Secondarily generalized seizures have a focus-one focal point of onset, unlike primarily generalized seizures, which apparently start all over the brain at the same time.


 What are epilepsy syndromes?

When a person’s seizure disorder has a characteristic group of features, it is called a syndrome. Syndromes have a cluster of symptoms or signs that define them. Some of the most common or well-defined epileptic syndromes are febrile seizures, infantile spasms, Lennox-Gastaut syndrome, Benign Rolandic epilepsy, juvenile myoclonic epilepsy, progressive myoclonic epilepsy, reflex epilepsies, temporal lobe epilepsy, and frontal lobe epilepsy.


 What is Status Epilepticus?

Seizures usually end naturally after a few seconds or minutes, but on rare occasions a seizure doesn’t stop. When a seizure goes on longer than 30 minutes, or repeats in a series, the person is in status epilepticus. This state of continuous seizure activity can happen with any type of seizure. Status epilepticus is considered a medical emergency.