Epilepsy is a brain condition defined by recurring, unprovoked seizures. About 24 million people worldwide live with it. A seizure itself is a burst of uncontrolled electrical activity in the brain that temporarily disrupts how nerve cells communicate, causing changes in movement, sensation, awareness, or behavior. Having a single seizure doesn’t mean you have epilepsy. The clinical threshold is typically two unprovoked seizures more than 24 hours apart, or one seizure combined with a high probability (60% or greater) of having another within the next 10 years.
What Happens in the Brain During a Seizure
Your brain runs on electrical signals passed between billions of nerve cells. These cells communicate using a careful balance of chemical messengers: some that encourage cells to fire and some that tell them to quiet down. In epilepsy, that balance breaks down. Clusters of neurons begin firing excessively and in sync, like a crowd all shouting at once instead of taking turns. This synchronized burst overwhelms normal brain activity and produces the outward symptoms we recognize as a seizure.
The specific symptoms depend entirely on where in the brain this electrical storm starts and how far it spreads. A burst confined to one small area might cause a brief twitch in your hand or a strange taste in your mouth. One that sweeps across the entire brain can cause loss of consciousness and full-body convulsions.
Types of Seizures
Seizures are classified by where they begin in the brain and whether they affect awareness.
Focal onset seizures start in one specific area. If you remain fully aware during the event, it’s called a focal aware seizure. You might experience unusual sensations, involuntary movements on one side of the body, or sudden emotions like fear or déjà vu. If your awareness becomes impaired, you may stare blankly, make repetitive movements like lip-smacking or hand-rubbing, and have little memory of what happened afterward.
Generalized onset seizures involve both sides of the brain from the start. The most dramatic type is the tonic-clonic seizure (previously called grand mal), where your muscles stiffen, you lose consciousness, and your body jerks rhythmically. But generalized seizures also include absence seizures, which look like brief staring spells lasting just a few seconds. These are especially common in children and can happen dozens of times a day without anyone noticing.
Sometimes doctors can’t determine where a seizure begins. These are classified as unknown onset and may be reclassified later once more information is available.
Common Causes and Triggers
Epilepsy has many possible causes. Structural damage from a head injury, stroke, or brain tumor can create areas of abnormal electrical activity. Genetic factors play a role in many cases, particularly in childhood-onset epilepsy. Brain infections, developmental differences present from birth, and autoimmune conditions can all lead to epilepsy. In roughly a third of cases, no identifiable cause is found.
For people already living with epilepsy, certain factors can lower the threshold for a seizure. The most commonly reported triggers include:
- Lack of sleep
- Stress
- Alcohol use
- Skipping anti-seizure medication or changing doses
- Flashing or flickering lights
- Dehydration and skipped meals
- Hormonal changes during the menstrual cycle
- Illness or fever
Tracking personal triggers is one of the most practical things you can do to reduce seizure frequency. Many people find that sleep deprivation is their most reliable trigger.
How Epilepsy Is Diagnosed
An EEG (electroencephalogram) is the primary tool. It records your brain’s electrical activity through sensors placed on your scalp. Doctors look for characteristic patterns called epileptiform discharges: sharp spikes and waves that signal abnormal electrical behavior. When these patterns are present between seizures, they confirm epilepsy with a sensitivity above 90%. Certain spike patterns are even specific to particular epilepsy types. For example, a three-per-second spike-and-wave pattern points to absence epilepsy.
Brain imaging, usually an MRI, helps identify structural causes like scarring, tumors, or developmental abnormalities. In some cases, doctors use video-EEG monitoring, where brain activity and physical behavior are recorded simultaneously over hours or days. This is particularly useful for distinguishing epileptic seizures from events that look similar but have different causes.
Not All Seizure-Like Events Are Epilepsy
Some people experience episodes that closely resemble epileptic seizures but have no abnormal electrical activity in the brain. These are called psychogenic non-epileptic events, and they’re more common than many people realize. They often arise from psychological distress, and anxiety, depression, and post-traumatic stress disorder are diagnosed more frequently in these patients. The distinction matters because anti-seizure medications won’t help, and the right treatment involves addressing the underlying psychological factors. Video-EEG monitoring is the definitive way to tell the two apart: during a psychogenic event, the EEG shows normal brain rhythms throughout.
Treatment With Medication
Anti-seizure medications are the first line of treatment and control seizures effectively in about two-thirds of people. These drugs work by calming excessive electrical activity in the brain through different mechanisms. Some slow down the firing of nerve cells by acting on sodium channels. Others reduce excitatory signaling or boost the brain’s natural inhibitory signals. The specific medication your doctor chooses depends on your seizure type, age, other health conditions, and potential side effects.
Finding the right medication often involves trial and adjustment. Some people respond well to the first drug tried. Others need to try two or three before finding one that controls seizures without intolerable side effects. Taking medication consistently is critical, as missed doses are one of the most common seizure triggers.
When Medication Doesn’t Work
About one-third of people with epilepsy continue to have seizures despite trying multiple medications. This is called drug-resistant epilepsy. For these individuals, other options exist. Surgery to remove or disconnect the brain area generating seizures is an option when that area can be precisely identified and safely targeted. Nerve stimulation devices that send mild electrical pulses to the brain can reduce seizure frequency in some people.
The ketogenic diet, a high-fat, very-low-carbohydrate eating plan, has shown meaningful results for drug-resistant epilepsy. In a randomized trial involving children, 38% on the diet experienced more than a 50% reduction in seizures after three months. A combined analysis of studies in adults found that over 53% achieved at least a 50% seizure reduction, and 13% became seizure-free. The diet appears to work through several pathways: it shifts the brain’s energy source in ways that stabilize nerve cell membranes, boosts the brain’s natural calming signals, and may even involve changes in gut bacteria that contribute to seizure control. The diet requires medical supervision and isn’t easy to maintain, but for some people it provides relief that medications could not.
What to Do if Someone Has a Seizure
If you witness someone having a convulsive (tonic-clonic) seizure, your role is to keep them safe while it runs its course. Turn the person onto their side to help keep their airway clear. Move furniture or sharp objects away from them. Time the seizure from the moment it starts.
Do not put anything in their mouth. It’s physically impossible to swallow your tongue during a seizure, and placing objects in the mouth risks breaking teeth or causing other injuries. Don’t try to hold the person down or restrain their movements. When the seizure ends, stay with them and offer calm reassurance, as confusion and disorientation afterward are normal. A seizure lasting more than five minutes is a medical emergency that requires calling 911.