There are 21 recognized types of seizures, organized into three main categories based on where they start in the brain: focal, generalized, and unknown. This classification system, maintained by the International League Against Epilepsy (ILAE) and most recently updated in 2025, also includes a fourth category for seizures that can’t yet be classified due to insufficient information. Within each category, seizures are further divided by whether they produce visible physical symptoms or primarily affect consciousness and internal experience.
The Three Main Categories
Every seizure classification starts with one question: where in the brain did the abnormal electrical activity begin? Focal seizures start on one side of the brain. Generalized seizures appear to begin on both sides simultaneously. When the starting point can’t be determined, either because no one witnessed the onset or because testing hasn’t been completed yet, the seizure falls into the unknown category. A fourth label, “unclassified,” is reserved for seizures that don’t fit neatly into any of the three even after full evaluation.
From there, each category branches into subtypes based on what actually happens during the seizure. Some involve obvious physical movements like stiffening, jerking, or shaking. Others affect awareness, sensation, or emotions without any visible signs at all. This layered system means two people can both have focal seizures but experience them in completely different ways.
Focal Seizures
Focal seizures begin in one specific area of the brain, and what you experience depends entirely on which area that is. A focal seizure starting in the part of the brain that processes vision might cause strange visual disturbances, while one starting in an area tied to emotion might trigger sudden, unexplained fear or déjà vu.
The most important distinction within focal seizures is whether consciousness is affected. In a focal aware seizure (previously called a simple partial seizure), you remain fully alert and can remember everything that happened. In a focal impaired consciousness seizure (previously called a complex partial seizure), your awareness drops during some or all of the event. Any decrease in awareness of yourself or your surroundings at any point during the seizure qualifies it as impaired consciousness. Some of these seizures begin with a fully aware phase, sometimes called an aura, before progressing to impair consciousness, particularly when they originate in the temporal lobe.
Whether someone was truly aware during a seizure is assessed by two things: whether they can recall events during the seizure and whether they were able to respond to instructions while it was happening.
Focal seizures can also spread. A focal seizure that begins on one side of the brain and then engages both sides is called a focal-to-bilateral tonic-clonic seizure. This looks identical to a generalized tonic-clonic seizure once it spreads, but it’s classified differently because of where it started.
Generalized Seizures
Generalized seizures engage both sides of the brain from the start and almost always involve some loss of consciousness. They split into two broad groups: motor and nonmotor.
Generalized Motor Seizures
These are seizures with visible muscle involvement. Muscles may stiffen, go limp, jerk, spasm, or shake, sometimes in combination. The most well-known type is the tonic-clonic seizure, formerly called a “grand mal” seizure. It involves an initial phase of full-body stiffening (the tonic phase) followed by rhythmic jerking (the clonic phase). Tonic-clonic seizures typically last a few minutes and often leave the person confused and exhausted afterward.
Other generalized motor subtypes include tonic seizures (stiffening only), clonic seizures (jerking only), atonic seizures (sudden loss of muscle tone, causing a person to drop or collapse), and myoclonic seizures (brief, lightning-fast jerks that can feel like an electric shock). Each of these can occur independently, and they vary widely in severity. A myoclonic jerk might look like nothing more than a sudden twitch, while an atonic seizure can cause a serious fall.
Generalized Nonmotor (Absence) Seizures
These are seizures with little or no visible movement. The classic example is the absence seizure, formerly called a “petit mal” seizure. Absence seizures cause brief, sudden lapses in consciousness, usually lasting just a few seconds. A person might stop mid-sentence, stare blankly, and then resume as if nothing happened. They’re so subtle they often go unnoticed by the person experiencing them and by bystanders.
Absence seizures come in two forms. Typical absence seizures are brief and stereotypical, meaning they look roughly the same each time. Atypical absence seizures are less predictable in pattern and usually last longer, sometimes stretching to a few minutes. The two types also show different patterns on brain wave recordings, with atypical absence seizures producing slower, less organized electrical activity.
Unknown Onset Seizures
Sometimes a seizure simply can’t be categorized as focal or generalized. This usually happens because no one saw the beginning, brain wave recordings weren’t available, or the results don’t point clearly in one direction. The “unknown” label isn’t a permanent diagnosis. It’s a placeholder that can be updated once more information is gathered.
Even within this category, seizures can still be described by their features. An unknown onset seizure with tonic-clonic movements is classified as unknown motor. One that mainly involves a pause in activity without obvious physical symptoms is classified as unknown nonmotor, sometimes called a behavior arrest seizure.
Special Situations: Febrile Seizures
Febrile seizures are triggered by fever in young children and fall outside the standard epilepsy classification because they aren’t caused by an underlying seizure disorder. They’re divided into simple and complex. A simple febrile seizure lasts 15 minutes or less, affects the whole body rather than one side, and happens only once within a 24-hour period. A complex febrile seizure lasts longer than 15 minutes, involves one side of the body more than the other, or occurs more than once in a day. Simple febrile seizures are far more common and are generally not associated with long-term problems.
When a Seizure Isn’t a Seizure
Not every event that looks like a seizure involves abnormal electrical activity in the brain. Psychogenic nonepileptic seizures (PNES) resemble epileptic seizures on the surface but show completely normal brain electrical activity during an episode. They’re caused by psychological factors rather than by misfiring neurons.
PNES can involve full-body shaking, loss of responsiveness, or unusual movements, but certain features tend to distinguish them: episodes that last longer than 10 minutes, out-of-sync limb movements, eyes that stay closed during unresponsiveness, and rapid side-to-side head shaking. The definitive diagnostic test is a video EEG, which records brain activity and physical behavior simultaneously. If brain waves remain normal during an episode, the event is functional rather than epileptic. This distinction matters because PNES requires a completely different treatment approach than epilepsy.
Status Epilepticus: When a Seizure Becomes an Emergency
Any seizure type can become dangerous if it doesn’t stop. Status epilepticus is defined as a seizure lasting longer than 5 minutes, or multiple seizures occurring within a 5-minute window without the person returning to full consciousness between them. This applies to both convulsive and nonconvulsive seizure types. It’s a medical emergency because prolonged seizure activity can cause brain damage, and the longer it continues, the harder it becomes to stop.