A seizure is a burst of uncontrolled electrical activity in the brain. Normally, brain cells fire in organized patterns, but during a seizure, large groups of neurons become overexcited and start firing simultaneously, amplifying the intensity of symptoms. Up to 10% of people worldwide will have at least one seizure during their lifetime, and a single seizure does not necessarily mean you have epilepsy or an ongoing condition.
What Happens in the Brain During a Seizure
Your brain runs on electrical signals. Neurons communicate by firing quick pulses of activity, then resting before the next one. During a seizure, something disrupts that rhythm. Neurons become hyperexcitable, meaning a single stimulation triggers a rapid-fire chain of electrical pulses with no rest period in between. Worse, nearby groups of neurons sync up and start firing at the same rate, a phenomenon called hypersynchrony. This wave of synchronized, runaway electrical activity is what produces the physical and mental symptoms you see from the outside.
Where that activity starts in the brain, and how far it spreads, determines what kind of seizure it is and what it looks like.
Focal Seizures: Starting on One Side
Focal seizures begin in one area on one side of the brain. They come in two forms, depending on whether awareness is affected.
In a focal aware seizure, the person stays conscious the whole time. They can sometimes talk during the episode and remember it afterward. Symptoms tend to be subtle: a sudden sense of déjà vu, a strange rising feeling in the stomach, or unusual movements on one side of the body. These are sometimes called “auras,” and people who have them regularly often recognize them as a warning sign.
A focal impaired awareness seizure is different. The person looks confused or dazed, may pick at their clothes, smack their lips, or stare blankly. They typically can’t respond to questions or follow directions for several minutes. Afterward, they often have no memory of what happened.
Either type of focal seizure can spread to both sides of the brain, at which point it causes loss of consciousness and movements on both sides of the body.
Generalized Seizures: Both Sides at Once
Generalized seizures begin, or appear to begin, on both sides of the brain simultaneously. They almost always cause a loss of consciousness or awareness.
Generalized motor seizures involve visible muscle activity. The most recognized type is the tonic-clonic seizure: muscles stiffen (the tonic phase), then begin rhythmic jerking (the clonic phase). The person may cry out, fall to the ground, and lose bladder control. Other variations include myoclonic seizures (brief, lightning-fast jerks) and atonic seizures (a sudden loss of muscle tone that causes the person to drop).
Absence seizures look nothing like what most people picture. They cause short, sudden lapses in consciousness, sometimes lasting only a few seconds. The person may stare blankly, blink rapidly, or make small chewing or hand movements. These are especially common in children and can happen dozens of times a day without anyone noticing.
One Seizure Does Not Mean Epilepsy
This is one of the most important distinctions to understand. A seizure is a single event. Epilepsy is a condition defined by recurring seizures. The standard threshold is two or more unprovoked seizures separated by at least 24 hours.
Many people have a single seizure and never have another. Seizures can be provoked by specific, identifiable causes: low or very high blood sugar, shifts in blood sodium or calcium levels, kidney or liver problems, high fever, eclampsia during pregnancy, heavy alcohol use, or alcohol withdrawal. When the trigger is treated or removed, the seizures stop. Unless there is underlying brain damage, a family history of epilepsy, or other neurological issues, most single seizures are not followed by additional ones.
Common Triggers That Lower the Threshold
For people who are susceptible to seizures, certain factors can make one more likely. The most commonly reported triggers include:
- Sleep deprivation or disrupted sleep patterns
- Stress, whether positive or negative
- Alcohol, particularly heavy use or withdrawal
- Flashing lights or visual patterns
- Missed meals, dehydration, or low blood sugar
- Hormonal changes, including the menstrual cycle
- Illness, with or without fever
- Missed medications for those already on anti-seizure treatment
- Recreational drugs, especially stimulants like cocaine
- Excess caffeine
What the Recovery Period Feels Like
The period immediately after a seizure is called the postictal state, and it catches many people off guard. You don’t just “snap back.” Your brain needs time to reset, and during that window, which lasts anywhere from five minutes to several days (the average is five to 30 minutes), you may feel confused, exhausted, sore, or unable to speak clearly. Headaches and memory gaps are common. Some people feel nauseous, and some lose bladder or bowel control during or after the event.
The emotional aftermath can be just as significant. Depression, anxiety, agitation, and embarrassment are all common postictal symptoms. Many people develop a fear of having another seizure in public, which can lead to social withdrawal. These feelings sometimes linger well beyond the physical recovery. In severe cases, people experience hallucinations, delirium, or suicidal thoughts during the postictal window.
How Seizures Are Diagnosed
After a first seizure, a doctor will typically start by taking a detailed history: what happened before, during, and after the event, how long it lasted, what movements occurred, and whether there was a loss of awareness. Eyewitness accounts are often more useful than the patient’s own memory, since many people don’t remember the seizure itself.
The most common test is an EEG, which measures electrical activity in the brain through sensors placed on the scalp. A routine EEG takes minutes to a couple of hours and can reveal abnormal electrical patterns, identify the type of seizure, and pinpoint where in the brain it originated. If the routine test comes back normal but seizures are still suspected, a prolonged EEG with video monitoring over several days in a hospital setting can capture an actual episode as it happens.
Brain imaging, most often an MRI, lets doctors look at the brain’s structure in detail to identify possible seizure-producing areas like scar tissue, tumors, or other structural changes. In more complex cases, specialized scans can map brain metabolism and blood flow to locate seizure-causing regions with greater precision.
What To Do if Someone Has a Seizure
If you witness a seizure, the most important thing is to keep the person safe and time the event. Ease them to the ground if they’re falling, turn them gently on their side with their mouth pointing toward the ground to keep the airway clear, and place something soft under their head. Loosen anything around the neck that could restrict breathing.
What you should not do matters just as much. Don’t hold the person down or try to stop their movements. Don’t put anything in their mouth: this is a persistent myth that leads to broken teeth and jaw injuries. Don’t attempt mouth-to-mouth breathing during the seizure, since people almost always resume breathing on their own. Don’t offer food or water until the person is fully alert.
Call 911 if the seizure lasts longer than five minutes, if the person doesn’t regain consciousness afterward, if it’s their first seizure, if they’re injured, or if they have difficulty breathing once the seizure stops. A seizure lasting beyond five minutes is a medical emergency that requires immediate intervention.