Seizures range from a blank stare to full convulsions, and neurologists sort them by origin
Not every seizure looks like the dramatic convulsions of film and television. Some are a few seconds of vacant staring, a sudden smell that isn't there, or an overwhelming sense of déjà vu. All share one cause: a burst of brain cells firing together too much, and roughly 50 million people worldwide live with the condition.
What a seizure looks like depends on where in the brain the surge happens. Motor effects include stiffening, rhythmic jerking, sudden twitches or an abrupt loss of muscle tone; others affect sensation, emotion, thinking or automatic body functions. Some people notice an aura first, such as a strange odour or emotional shift. Most episodes end within two minutes and are followed by a recovery phase of confusion or tiredness. One lasting over five minutes, or several in a row without recovery in between, is classed as status epilepticus, a medical emergency.
In 2025 the International League Against Epilepsy updated its classification into four groups. Focal seizures start in a network confined to one hemisphere, usually in the same spot each time, though they can spread to both sides. Generalized seizures begin at one point but rapidly engage both hemispheres; they include absence seizures, brief lapses of awareness, and tonic–clonic seizures, once called grand mal, which carry the greatest risk. The last two groups cover cases where the origin is unknown or information is too thin to classify.
Doctors also ask whether a seizure was provoked. Fever in children, low blood sugar or sodium, brain infections, strokes, head injuries and alcohol withdrawal can all trigger one in someone without a lasting tendency. Unprovoked seizures have no immediate cause and reflect an underlying predisposition, from brain malformations and tumours to genetic syndromes such as Dravet syndrome. Some, called reflex seizures, reliably follow a stimulus like flashing lights.
Epilepsy is diagnosed after two unprovoked seizures more than 24 hours apart, or after one if tests suggest at least a 60% chance of another within 10 years. Among patients older than one, focal seizures with impaired awareness are the most common type, affecting 36% overall.
Source: Seizure
