There are many types of seizures. The names can be confusing, since patients (and even doctors) can sometimes use the terms loosely. Seizures can be divided into three main categories:
Partial Onset (also known as focal or localization-related)
The abnormal electrical activity starts in a limited area of the brain.
- Simple partial seizure: The abnormal activity remains limited, causing a change in function of a limited part of the brain (manifested as altered vision, speech, emotion, sensation or motor activity without loss of consciousness.
- Complex partial seizure: Abnormal activity spreads through a larger area of brain, causing confusion and change in awareness.
- Secondarily generalized seizure: Abnormal activity can sometimes spread to all of the brain, resulting in loss of consciousness, falling, and convulsions of the body. Some people call this "grand mal" or "generalized tonic clonic" seizure, but these names are also used to describe seizures that are of generalized, rather than localized, onset (see below).
General Onset (also known as primary generalized)
The abnormal electrical activity starts throughout the entire brain all at once. Seizure types in this category include.
- Generalized tonic clonic: This type of seizure causes loss of consciousness, falling, and convulsions of the body, with the abnormal brain activity starting all over at once.
- Absence: Usually seen in children, this causes brief loss of consciousness and staring. This type of seizure used to be called "petit mal".
- Myoclonic: This type of seizure causes sudden, brief muscle jerks. There are, however, other causes of myoclonus which are not related to epilepsy.
- Tonic: This is characterized by sudden bilateral flexion or extension of the trunk, arms, and/or legs.
Other Seizure Types
- Febrile Seizures: These are generalized convulsions in the context of fever which occur in childhood in about 5% of the U.S. population. Most children who experience febrile seizures are not at increased risk of epilepsy in the future.
- Provoked seizures: Seizures which occur because of some immediate and brief insult to the brain are considered to be different from the recurrent seizures of epilepsy. An example would be alcohol withdrawal seizures or seizures due to the side effect of a medication.
Other non-neurological and neurological disorders can come and go and mimic seizures. Examples are circulatory disorders such as fainting (syncope), cardiovascular disorders, movement disorders, sleep disorders, migraine disorders, or psychiatric disorders.