Seizures take many forms. Before your doctor can prescribe the right treatment, he or she must figure out which type (or types) you have. That's the purpose of all the tests discussed in the Diagnosis section—not just to tell whether you have epilepsy but also to tell what kind.

There are so many kinds of seizures that neurologists who specialize in epilepsy are still updating their thinking about how to classify them. Usually, they classify seizures into two types, primary generalized seizures and partial seizures. The difference between these types is in how they begin:

Primary generalized seizures

Primary generalized seizures begin with a widespread electrical discharge that involves both sides of the brain at once. Hereditary factors are important in many of these seizures.

Partial seizures

Partial seizures begin with an electrical discharge in one limited area of the brain. Some are related to head injury, brain infection, stroke, or tumor, but in most cases the cause is unknown.

One question that is used to further classify partial seizures is whether consciousness (the ability to respond and remember) is "impaired" or "preserved." The difference may seem obvious, but really there are many degrees of impairment or preservation of consciousness.

Identifying certain seizure types and other characteristics of a person's epilepsy like the age at which it begins, for instance, allows doctors to classify some cases into epilepsy syndromes. This kind of classification helps us to know how long the epilepsy will last and the best way to treat it.

Click on the names below for descriptions and details about each type:

Primary Generalized Seizures

• Absence seizures
• Atypical absence seizures
• Myoclonic seizures
• Atonic seizures
• Tonic seizures
• Clonic seizures
• Tonic-clonic seizures

Partial Seizures

• Simple partial seizures
• Complex partial seizures
• Secondarily generalized seizures

Topic Editor: Steven C. Schachter, M.D.
Last Reviewed:12/15/06