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Bayfront Institute of Neurosciences Comprehensive Epilepsy Program |
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Types of Seizures
Seizure types are classified by the site of origin in the brain. Two main categories of seizures are
Partial (Focal) Seizures and Generalized Seizures.
Partial Seizures A partial seizure involves a localized area in one hemisphere of the brain, and is categorized as simple or complex.
Types of experiences in a simple partial (focal) seizure include but not limited to: seeing flashing lights, tingling in an arm or leg, jerking of a limb, feeling of fear or dread, sensing an unpleasant odor or a rising sensation in the stomach. This type of seizure is also known as an “aura,” and often serves as a warning that a bigger seizure may follow.
In a complex partial seizure, the areas of the brain controlling awareness are affected. Typically, a person having a complex partial seizure will have a blank stare and may perform automatic semi-purposeful movements such as lip smacking, picking at one’s clothes, or wandering about aimlessly and confused. During a complex partial seizure, a person’s ability to speak, understand, remember and respond fully is usually affected.
Generalized Seizures This kind of seizure occurs in large areas of the brain, often in both hemispheres and may be convulsive or non-convulsive. The two most common types are tonic clonic and absence, however other forms exist such as myoclonic, tonic, atonic, atypical absence and clonic seizures.
Tonic clonic seizure is the type of convulsive seizure that most people associate with epilepsy. The seizure usually begins with the tonic phase, in which the muscles of the body stiffen. This phase is immediately followed by the clonic phase in which the limbs, body, and head begin to jerk rhythmically. A tonic clonic seizure usually lasts for 1-2 minutes, during which the individual is unconscious.
Absence seizures occur most often in children, usually between the ages of 4-12. However, they can also occur in adolescence and adults. This type of seizure generally lasts less than 10 seconds. It is characterized by a “glazed” or “blank” look that begins and ends abruptly without any warning. Or the eyes will roll back and the eyelids will flutter briefly. Following this seizure, the person recovers immediately and is usually able to continue the activity that they were involved in.
Atypical Absence seizure is similar to an absence seizure except that the seizure onset and end is more gradual and obvious to a casual observer. This seizure type often occurs in some developmentally disabled individuals who have numerous seizure types, and can occur as part of the “Lennox-Gastaut Syndrome”.
Myoclonic Seizure consists of a sudden, brief shock-like jerks of the face, trunk, arms and or legs without loss of consciousness. They can be isolated or occur in rapid succession. This seizure type can be part of the syndrome of Juvenile Myoclonic Epilepsy or can be acquired due to brain injury.
Clonic Seizure is similar to a tonic-clonic seizure except that there is no tonic component.
Tonic Seizure consists of forceful tonic movement of the head forward often but not always accompanied by forceful elevation and extension of the arms forward and rigid extension of the legs.
Atonic Seizure consists of a sudden loss of muscle tone that may consist of a momentary drop of the head, the jaw, a limb or loss of all muscle tone leading to slumping to the ground. If consciousness is lost, it is usually brief.
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