Epilepsy is a brain disease that causes recurring, unprovoked seizures. Around 50 million people worldwide live with it, making it one of the most common neurological conditions on the planet. A seizure itself is a burst of uncontrolled electrical activity in the brain that temporarily changes how you move, feel, or behave. Having a single seizure doesn’t mean you have epilepsy, but when seizures keep happening, epilepsy is the likely diagnosis.
What Happens in the Brain During a Seizure
Your brain runs on electrical signals. Neurons fire in coordinated patterns to control everything from walking to thinking to breathing. During a seizure, two things go wrong at the cellular level: neurons become hyperexcitable, meaning they fire far more easily than normal, and they become hypersynchronous, meaning large groups of neighboring neurons get recruited into the same abnormal firing pattern at the same time.
Think of it like a stadium crowd. Normally, people talk in small groups. During a seizure, it’s as if hundreds or thousands of people suddenly start chanting the same thing in unison. This synchronized electrical storm disrupts the brain’s normal function, producing the visible symptoms of a seizure: muscle jerking, loss of awareness, unusual sensations, or a temporary blackout. What the seizure looks like depends entirely on where in the brain the abnormal firing starts and how far it spreads.
How Epilepsy Differs From a Single Seizure
Many people have a seizure once in their life and never have another. Epilepsy is diagnosed when the pattern suggests an ongoing risk. Specifically, it’s defined by any of these criteria:
- Two or more unprovoked seizures occurring more than 24 hours apart
- One unprovoked seizure combined with at least a 60% chance of another seizure within the next 10 years (based on brain imaging, EEG results, or other risk factors)
- A recognized epilepsy syndrome identified by a specific pattern of seizure types, age of onset, and test results
The word “unprovoked” matters. A seizure triggered by an obvious, temporary cause, like extremely low blood sugar, a high fever in a young child, or acute alcohol withdrawal, doesn’t count toward an epilepsy diagnosis. Epilepsy means the brain has a lasting tendency to generate seizures on its own.
Types of Seizures
Seizures fall into two main categories based on where the abnormal electrical activity begins.
Focal Onset Seizures
These start in one specific area of the brain, in just one hemisphere. What you experience depends on which part of the brain is affected. A focal seizure in the area that controls your hand might cause your fingers to twitch uncontrollably. One in the temporal lobe might produce a sudden wave of fear, a strange taste, or a dreamlike feeling of déjà vu.
Focal seizures are further divided by whether you remain aware during them. In a focal aware seizure, you know what’s happening even though you can’t stop it. In a focal seizure with impaired awareness, you may stare blankly, fumble with your clothes, or make repetitive movements like lip-smacking without realizing it. Some focal seizures spread from one hemisphere to both sides of the brain, producing a full-body convulsion. This is called a focal to bilateral tonic-clonic seizure.
Generalized Onset Seizures
These involve both hemispheres of the brain from the very start. The most dramatic type is the tonic-clonic seizure (formerly called grand mal), where the body stiffens, the person falls, and the muscles jerk rhythmically. But generalized seizures also include absence seizures, which look like brief staring spells lasting just a few seconds. Absence seizures are especially common in children and can happen dozens of times a day, sometimes mistaken for daydreaming.
When doctors can’t determine where a seizure begins, it’s classified as unknown onset. This doesn’t mean the seizure is mysterious, just that there wasn’t enough information (from observation or testing) to pin down the starting point.
What Causes Epilepsy
Epilepsy has six recognized categories of causes, and many people have more than one contributing factor.
- Structural: Physical changes in the brain, such as damage from a stroke, traumatic brain injury, brain tumor, or abnormal brain development before birth
- Genetic: Inherited gene mutations or spontaneous genetic changes that affect how neurons function. Some epilepsy syndromes run clearly in families, while others involve new mutations
- Infectious: Brain infections like meningitis, encephalitis, or neurocysticercosis (a parasitic infection common in some parts of the world)
- Metabolic: Conditions that alter the brain’s chemical environment, including disorders of amino acid metabolism or mitochondrial diseases
- Immune: Autoimmune conditions where the body’s immune system attacks brain tissue
- Unknown: In a significant number of cases, no clear cause is ever identified
Common Seizure Triggers
Having epilepsy means your brain has a lower threshold for seizures, but certain factors can push you past that threshold on any given day. The most common trigger is sleep deprivation. Overtiredness, disrupted sleep, or simply not sleeping enough can significantly raise seizure risk. Stress, both positive and negative, is another frequent trigger.
Other well-known triggers include heavy alcohol use or alcohol withdrawal, flashing or flickering lights (called photosensitivity), illness with or without fever, hormonal changes tied to the menstrual cycle, skipping meals or becoming dehydrated, excessive caffeine, recreational drug use, and missed doses of seizure medication. Many people with epilepsy learn their personal trigger patterns over time, which helps with day-to-day management.
How Epilepsy Is Diagnosed
Diagnosis starts with a detailed account of what happened during the seizure, ideally from both the person who experienced it and someone who witnessed it. From there, two key tests help confirm the diagnosis and guide treatment.
An electroencephalogram (EEG) records the brain’s electrical activity through sensors placed on the scalp. It can reveal characteristic patterns that identify the seizure type and pinpoint where seizures originate. Some people need extended EEG monitoring with video, especially if seizures are subtle, happen at night, or are hard to observe in real time.
Brain imaging, most commonly an MRI, looks for structural abnormalities that could be causing seizures: scar tissue, tumors, malformations, or evidence of past strokes. MRI provides much more detail than a CT scan. If surgery becomes a possibility, specialized imaging like functional MRI (which maps critical areas for speech and movement) or magnetoencephalography (which tracks magnetic fields produced by brain activity) can help surgeons plan a precise approach. Accurately identifying the seizure type and its origin gives you the best chance of finding effective treatment.
Treatment and Seizure Control
Anti-seizure medications are the first-line treatment for epilepsy. Under appropriate treatment, roughly 70% of people with epilepsy can become seizure-free. That’s the optimistic number. In real-world surveys, the picture is more complicated: among adults actively taking epilepsy medication, only about 44% reported being seizure-free in the past year. The gap between what’s theoretically possible and what actually happens reflects challenges like finding the right medication, managing side effects, and maintaining consistent access to care.
For people whose seizures don’t respond to medication (called drug-resistant epilepsy), other options include surgery to remove or disconnect the brain area where seizures start, devices that stimulate specific nerves to reduce seizure frequency, and specialized diets like the ketogenic diet. Treatment is highly individual, and finding the right approach often takes time and adjustment.
What to Do if Someone Has a Seizure
If you witness a tonic-clonic seizure (the kind with falling and convulsions), the goal is to keep the person safe, not to stop the seizure itself.
- Ease them to the ground if they’re falling
- Turn them gently onto one side with their mouth pointing toward the ground to keep the airway clear
- Clear away nearby objects that could cause injury
- Place something soft and flat under their head
- Remove their glasses and loosen anything tight around their neck
- Time the seizure
Never put anything in their mouth, and don’t try to hold them down. Most seizures end on their own within one to three minutes. If a seizure lasts longer than five minutes, or if the person has multiple seizures without regaining consciousness between them, that’s a medical emergency called status epilepticus, and you should call 911 immediately.