Seizure
A sudden disruption of brain activity from excessive neuronal firing.
Wikipedia / Wikimedia Commons
A seizure is a sudden event where brain activity becomes chaotic, triggered by a burst of excessive, synchronized firing of neurons, leading to altered behavior. This common neurological issue affects roughly 50 million people globally. Seizures are split into two categories: provoked, where a clear trigger like fever, a head injury, or a metabolic problem is present, and unprovoked, where no immediate cause is found. When unprovoked seizures happen repeatedly, the condition is known as epilepsy.
**Signs and symptoms** The observable signs and symptoms of a seizure are called seizure semiology, which shifts based on which brain regions are involved and the seizure type. These can affect movement, sensation, automatic body functions, or thinking and emotions. Motor signs include muscle stiffening (tonic activity), rhythmic jerking (clonic activity), sudden muscle twitches (myoclonus), a sudden loss of muscle tone (atonia), eye deviation, or other repetitive, involuntary movements (automatisms). Sensory issues might involve tingling, visual disturbances, vertigo, or hearing sounds that aren't there. Autonomic symptoms can include changes in heart rate, breathing, or stomach sensations. Cognitive or emotional effects may show up as confusion, fear, altered perception, or memory quirks like a strong sense of familiarity (déjà vu). Some people with focal seizures experience an aura—subjective feelings such as odd smells, a sudden mood shift, or déjà vu. Most seizures last under two minutes and are followed by a recovery phase called the postictal state, marked by confusion, fatigue, or other neurological symptoms. If a seizure lasts longer than five minutes, or if multiple seizures happen without full recovery in between, it's called status epilepticus—a medical emergency that can cause lasting brain damage or death.
**Classification** Seizures are categorized by where they start in the brain, their clinical features, and the person's level of consciousness during the episode. In 2025, the International League Against Epilepsy (ILAE) updated the classification to include four main types: focal, generalized, unknown whether focal or generalized, and unclassified. They are further sorted by whether consciousness is preserved or impaired, based on awareness and responsiveness during the event.
Quick Facts
- Field
- Neurology, emergency medicine
- Symptoms
- Variable
- Duration
- Typically less than 2 minutes
- Diagnosis
- Based on symptoms, blood tests, medical imaging, electroencephalography
- Differential
- Syncope, psychogenic seizure, migraine aura, transient ischemic attack
- Treatment
- Less than 5 min: Place person on their side, remove nearby dangerous objects / More than 5 min: Treat as status epilepticus
- Frequency
- ≈10% of people (lifetime risk)
- Complications
- Falling, drowning, car accidents, pregnancy complications, emotional health issues
- Types
- Focal, generalized; provoked, unprovoked
Facts from the source article.
Lore & Background
Seizures result from excessive, synchronized neuronal firing in the brain, leading to changes in movement, sensation, behavior, awareness, or consciousness. Symptoms vary widely: some involve subtle lapses in attention (absence seizures), while others cause generalized convulsions with loss of consciousness (tonic–clonic seizures). Most seizures last less than two minutes and are followed by a postictal period of confusion or fatigue. Status epilepticus, a seizure lasting longer than five minutes or multiple seizures without recovery, is a medical emergency that can cause long-term brain injury or death.
Reader's Guide
Seizures are classified by the International League Against Epilepsy (ILAE) into four major types: focal, generalized, unknown whether focal or generalized, and unclassified. Focal seizures originate in one hemisphere and may spread; they are subdivided by whether consciousness is preserved or impaired. Generalized seizures quickly spread across both hemispheres and include absence seizures, tonic–clonic seizures, and other motor and non-motor types. Provoked seizures are caused by transient conditions such as metabolic disturbances, infections, acute brain injuries, substance-related factors, or fever. Unprovoked seizures reflect an underlying neurological predisposition and meet epilepsy criteria when two or more occur more than 24 hours apart, or one with a recurrence risk of at least 60% over 10 years. Understanding seizure type and cause guides treatment and recurrence risk assessment.
Did You Know?
- Seizures affect approximately 50 million individuals worldwide.
- Status epilepticus is a medical emergency defined by a seizure lasting longer than five minutes or multiple seizures without full recovery.
- Focal impaired consciousness seizures are the most common type in individuals older than one year, affecting 36% of epilepsy patients.
More in Symptoms and signs 1-24
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