The International League Against Epilepsy (ILAE) is a scientific organization devoted to improving the lives of those living with epilepsy by promoting research, education, and training. They have recently developed a new way of classifying seizures to help us better diagnose and treat epilepsy. The new system has new terms for seizures that didn’t fit in the old classification, found in the graphic below:
“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 three main categories: Focal, Generalized or Unknown Onset. The category is determined by the location of the seizure activity within the brain at the beginning of the seizure. Seizures may also be described as either motor or nonmotor, depending on whether or not muscle movement is involved. In people younger than age 40, about 50% of new cases of epilepsy are generalized seizures, and 50% are partial.
What are Focal seizures?
Focal 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, focal seizures may or may not alter consciousness or awareness. The location of the seizure activity in the brain will determine what the seizure will look or feel like.
For example, a focal seizure in the part of the brain responsible for hearing could cause a sudden but temporary distortion in sound or the person could hear a sound that isn’t there (i.e. an auditory hallucination). A focal seizure in the part of the brain responsible for controlling finger movements could cause a sudden twitching of one or more fingers on the opposite side of the body.
Focal seizures can vary a lot from on person to another because of the wide range of functions that our brains control. However, an individual with a single seizure focus usually has the same experience each time their seizure starts.
Focal seizures that do not alter consciousness are called “Focal Aware” seizures. The person having the seizure is aware of what is happening. A focal aware seizure usually lasts only a short time. This type of seizure is also known as an “aura” if they experience things that are not visible to others such as an unusual feeling, and it often serves as a warning that a bigger seizure will follow.
Focal aware 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.
For example, if the abnormal electrical burst occurs in a specific part of the brain responsible for vision, the focal aware seizure may consist of seeing flashing lights. If it is on the brain’s sensory strip, the person may experience a tingling arm or leg; on the motor strip, their limb may 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 Focal Impaired Awareness seizures?”
Focal impaired awareness seizures involve deep, central structures of the brain controlling consciousness, so awareness and/or thinking abilities are altered or lost.
A focal impaired awareness seizure may begin as a focal aware 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 focal impaired awareness seizure typically stares blankly, and performs automatic, unconsciously repeated movements, such as lip smacking, picking at one’s clothes, or rearranging objects. These movements are called “automatisms”. Some people wander around, aimless and confused. 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 often does not recognize it as epilepsy. Some people who exhibit unusual behaviours while having a focal impaired awareness seizure could be mistaken for being under the influence of alcohol or drugs, and could be mistakenly viewed as uncooperative/mishandled.
What is an aura?”
An aura is another name for a focal aware seizure, a sensory experience driven by a seizure in that sensory part of the brain. It often serves as a warning that a bigger seizure will follow.
“What are Generalized seizures?”
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 quickly spread across the left and right hemispheres of the brain. Many, but not all, generalized seizures are associated with a loss of consciousness. They can be convulsive or non-convulsive.
Most generalized seizures cause changes in the body’s muscles, such as a stiffening of the muscles (tonic), a decrease in muscle tone (atonic), rhythmic jerking movements (clonic), or a sudden twitch or jolt-like movement (myoclonic). These various types of muscular changes are associated with different types of generalized seizures, as listed below, but could occur during focal seizures too.
There are six main types of generalized seizures: Generalized or Unknown Onset Tonic-Clonic, Generalized Absence, Clonic, Tonic, Focal or Generalized Atonic, and Focal or Generalized Myoclonic.
Fact: Generalized seizure activity occurs in the bumpy outer layer of the brain, known as the cortex, but does not always involve the entire cortex. There may also be seizure activity in some of the deeper brain structures underneath the cortex.
“What are Generalized or Unknown Onset Tonic-Clonic Seizures?”
This is the type of convulsive seizure that most people recognize as epilepsy.
These seizures usually begin 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 may be difficult because of the stiffened chest muscles, and, with the change in available oxygen, the skin colour may turn 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 generalized or unknown onset 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 sore for a period of minutes or hours afterwards, and should be allowed to rest until they have fully recovered.
“What are Generalized Absence Seizures?”
These seizures are very brief, about 9 seconds on average. The most striking feature is a blank or vacant look that could be misinterpreted as a brief episode of daydreaming. The blank look may be the only outward sign, although some people have other features that could include eye movements, blinking or automatic behaviours.
A generalized absence seizure would typically start abruptly and end abruptly. After the brief seizure, the person will generally carry on with whatever they had been doing before. These seizures can go unnoticed, or, if noticed, they may not be recognized as being a seizure. Generalized absence seizures can be typical, atypical, myoclonic, or with eyelid myoclonia.
Generalized absence seizures can go unnoticed, or, if noticed, they may not be recognized as being a seizure. 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.[/expand]
“What are Clonic Seizures?”
These seizures cause rhythmic jerking movements. When the rhythmic jerking movements are the only feature, it is a clonic seizure. These types of movements occur more frequently in association with a phase of muscle stiffening (see tonic-clonic seizures above). These seizures may also have a focal onset.
“What are Tonic Seizures?”
These seizures cause the muscles to stiffen. If a person is standing, a sudden increase in muscle tone could cause them to fall. Some people call this a “drop attack”. Generalized tonic seizures could also cause a sudden stiffening (or contraction) of the muscles in both arms. These seizures usually last less than 20 seconds, but sometimes they could be up to about 60 seconds. These seizures may also have a focal onset.
“What are Focal or Generalized Atonic Seziures?
These seizures cause a loss of muscle tone, which means the individual suddenly becomes limp. If a person is standing, the sudden loss of muscle tone will cause them to fall. Therefore, both tonic seizures and atonic seizures can be associated with episodes that people may refer to as drop attacks.
These seizures may also have a focal onset.
“What are Focal or Generalized Myoclonic Seizures?”
The name myoclonic comes from a combination of two terms: myo meaning muscle and clonic meaning jerk. These seizures are extremely brief, jolt-like movements that resemble a startle response. For example, an individual could have a sudden jerk of their upper arms or shoulders. Sometimes the muscle contractions are subtle and may not be visible to an observer.
These seizures are usually less than a second in length. They may also have a focal onset.
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 Secondarily Generalized Seizures?”
Secondarily generalized seizures begin as focal seizures. They start in part of the brain as an aura (a focal aware seizure) or as a change in awareness (a focal impaired awareness 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.
Questions to ask your healthcare provider about your seizures:
- Do I have focal seizures or generalized seizures, or both?
- Which seizure type (or types) do I have?
- When would a seizure be a medical emergency for me?