Types of Seizures: Focal, Generalized, and Unknown

This article is educational and is not medical advice. It does not diagnose, treat, prevent, or cure any condition. Komori is not a medical device, is not FDA-cleared, does not detect seizures, and is not intended for people with epilepsy. Talk with a neurologist or epileptologist about personal medical decisions. Households living with epilepsy should use clinically validated seizure-detection devices as directed by their care team.

If you grew up hearing "grand mal," "petit mal," or "partial seizure," you are not using the wrong idea. You are using the old names.

Clinicians classify seizures by where they start in the brain, then by what happens next. The International League Against Epilepsy rebuilt that language in 2017. CDC's public types page follows it.

I'm not a clinician. This page is a glossary. Only a neurologist can classify a person's seizures.

Why they changed the names

The ILAE 2017 position paper, led by Robert S. Fisher, is an operational classification. The authors said current knowledge was not enough for a purely scientific taxonomy, so they built a practical one on top of the 1981 system.

Some seizure types, tonic seizures or epileptic spasms, can start as either focal or generalized. The 1981 system had no clean place for an event whose start no one saw. Terms like "partial," "simple partial," "complex partial," and "dyscognitive" did not travel well outside a clinic. "Partial" sounds like part of a seizure. "Complex" sounds like the hard kind. Neither helps a parent in a waiting room.

So they swapped the labels. Partial becomes focal. Awareness becomes a classifier for focal seizures. Simple partial becomes focal aware. Complex partial becomes focal impaired awareness. Secondarily generalized becomes focal to bilateral tonic-clonic. Grand mal maps to generalized tonic-clonic, or to unknown-onset tonic-clonic, or to focal to bilateral tonic-clonic, depending on how it started. Petit mal maps to absence.

The first cut: where it starts

ILAE 2017 divides seizures into three onset groups.

Focal onset. Activity starts in networks limited to one hemisphere. It can be a tiny patch or a wider stretch of that hemisphere. CDC calls these focal seizures or focal onset seizures. They can change awareness, behavior, or sensation, or cause movements that are usually on one side of the body. NINDS states that about 60 percent of people with epilepsy have focal seizures.

Generalized onset. Activity starts at some point within, and rapidly engages, bilaterally distributed networks. CDC says these usually cause a loss of consciousness or awareness and may cause movements on both sides of the body. The movements do not have to be perfectly symmetric.

Unknown onset. The start was missed. The person was asleep, alone, or everyone in the room was watching the dramatic part. ILAE 2017 lets a clinician still name features that were seen, such as tonic-clonic movements, without pretending to know the origin. Unknown onset is a placeholder for ignorance, not a personality trait of the seizure. Later information can move it into focal or generalized.

ILAE told clinicians to call a seizure focal or generalized only with high confidence. The paper uses an 80 percent threshold as a practical cutoff. Below that, it stays unknown until more information arrives. A person can have more than one type.

Awareness, in the 2017 sense

For focal seizures, ILAE 2017 uses awareness as an optional classifier.

Retained awareness means the person is aware of self and environment during the seizure, even if they cannot move. A focal aware seizure is the current name for what used to be called a simple partial seizure.

Impaired awareness during any part of the seizure makes it a focal impaired awareness seizure. That's the current name for a complex partial seizure. Any part. Not "most of it." Any part.

Awareness is not the same as being able to talk or follow commands. Some people are immobile and unresponsive and still later recall who walked into the room. If awareness cannot be determined, "focal seizure" is still a complete name.

Focal vs generalized, in English

CDC splits focal seizures by awareness, which matches ILAE.

Focal onset aware seizures. The person does not lose awareness. They may be able to talk and later remember the event. CDC lists déjà vu, a funny feeling in the stomach, and abnormal movements. NINDS adds sudden unexplained emotions and seeing, hearing, smelling, tasting, or feeling things that are not there. Some people have an aura. In clinic language, that unusual sensation is itself the start of the seizure.

Focal impaired awareness seizures. Awareness is lost. CDC lists looking confused or dazed, picking at clothes, lip-smacking, and being unable to respond for a few minutes. NINDS calls those repeated, often purposeless movements automatisms. They usually last no more than a minute or two.

A focal seizure can spread to both hemispheres. ILAE 2017 named that pattern focal to bilateral tonic-clonic. It replaced "secondarily generalized."

Tonic-clonic is the generalized type most people picture. Muscles stiffen, then jerk in a rhythm. The person usually loses consciousness. CDC says these usually last a few minutes and can leave the person confused and tired. Old name: grand mal.

CDC and ILAE share the motor vocabulary. Tonic means stiff. Clonic means rhythmic jerking. Myoclonic means short, lightning-quick jerks. Atonic means a sudden loss of tone, which can cause a fall.

Generalized nonmotor seizures are the absence group. CDC says they cause short, sudden lapses of consciousness and often go unnoticed. Old name: petit mal. Someone may stare, blink quickly, or make chewing or hand movements.

ILAE 2017 also added generalized types the 1981 list was missing: absence with eyelid myoclonia, myoclonic absence, myoclonic-atonic, and myoclonic-tonic-clonic. Those names matter in a clinic. They are not DIY labels.

Seizure type is not epilepsy type

This is the part people skip, then get surprised in the clinic.

ILAE's 2017 classification of the epilepsies sits on top of seizure type. After the seizure is named, the clinician names the epilepsy type: focal epilepsy, generalized epilepsy, combined generalized and focal epilepsy, or unknown. Then, when they can, they name a syndrome and they keep looking for a cause.

Scheffer and colleagues split causes into structural, genetic, infectious, metabolic, immune, and unknown. You do not need all three levels on day one.

If you see a seizure of any type last more than 5 minutes, or the person does not wake fully between seizures, CDC says call 911.

FAQ

What are the three main ILAE seizure groups?

Focal onset, generalized onset, and unknown onset. ILAE 2017 sorts first by where the seizure starts. CDC's public page uses the same split for focal and generalized.

What did simple partial and complex partial become?

Simple partial became focal aware. Complex partial became focal impaired awareness. Impaired awareness during any part of a focal seizure makes it the impaired-awareness type.

What is the new name for grand mal?

Grand mal maps to generalized tonic-clonic if it started on both sides, focal to bilateral tonic-clonic if it started on one side and spread, or unknown-onset tonic-clonic if nobody saw the start.

Can someone have more than one seizure type?

Yes. CDC says a person with epilepsy can have more than one type. ILAE's epilepsy classification even has a combined generalized and focal epilepsy group for people who have both.

Sources

• Fisher et al., Operational classification of seizure types by the ILAE, Epilepsia (2017): https://www.ilae.org/files/dmfile/Operational-Classification--Fisher_et_al-2017-Epilepsia.pdf
• Fisher et al., Instruction manual for the ILAE 2017 operational classification of seizure types, Epilepsia (2017): https://www.ilae.org/files/dmfile/Operational-Classification---Instruction-manual-Fisher_et_al-2017-Epilepsia-1.pdf
• Scheffer et al., ILAE classification of the epilepsies, Epilepsia (2017): https://www.ilae.org/files/dmfile/ClassificationOfEpilepsies_Scheffer_et_al-2017-Epilepsia.pdf
• CDC, Types of Seizures: https://www.cdc.gov/epilepsy/about/types-of-seizures.html
• NINDS, Epilepsy and Seizures: https://www.ninds.nih.gov/health-information/disorders/epilepsy-and-seizures

Related reading: What is epilepsy vs a seizure and tonic-clonic seizures.