Epilepsy and seizures

A seizure is one of the most frightening things to witness and one of the most ordinary things the brain can do when it loses its rhythm. Epilepsy — the tendency to have seizures over and over — is among the most common serious neurological conditions in the world, affecting roughly 50 million people, and yet it is still wrapped in fear and old superstition. The aim of this page is to take the mystery out of it from first principles: what a seizure actually is at the level of brain cells, the different kinds and what they look like, what causes epilepsy and what sets seizures off, how doctors diagnose it, and the genuinely good news on treatment — most people with epilepsy can become seizure-free. It is written for anyone: someone newly diagnosed, a worried parent or partner, a teacher or colleague, or simply the curious. Before anything else, the single most useful thing to know is what to do if you see a seizure, so we start there.

What a seizure actually is

The brain runs on electricity. Around 86 billion neurons signal to one another with tiny, precisely timed electrical and chemical pulses, and in normal working they fire in a busy but orchestrated way — different groups active at different moments, held in check by the brain's own braking signals. A seizure is what happens when that order breaks down: a population of neurons suddenly fires together, excessively and in lockstep — a burst of abnormal, hypersynchronous electrical activity. Normally the “slow down” signals (chiefly the neurotransmitter GABA) keep excitation in balance. In a seizure that balance tips towards runaway excitation, and the brain region involved — or, in a big seizure, much of the brain at once — is briefly hijacked.

Because the brain does everything, a seizure can look like almost anything, depending on which part is misfiring: a strange smell or a rising feeling in the stomach, a twitch in one hand, a few seconds of blankness, or the full-body convulsion most people picture. The outward event is just the electrical storm made visible.

A crucial distinction underlies the whole subject. A single seizure is not the same as epilepsy. Many seizures are provoked — caused by an obvious, temporary insult to a normal brain, such as a very high fever in a small child, dangerously low blood sugar or sodium, a head injury, or alcohol withdrawal (more on that below, and in the companion guide to alcohol). Remove the cause and the seizures stop. Epilepsy is diagnosed when someone has a tendency to recurrent, unprovoked seizures — the brain itself is primed to seize without a one-off trigger. In practice that usually means two or more unprovoked seizures, or one seizure plus clear evidence (on a scan or an EEG) that more are likely.

Types of seizure

The first and most useful question about any seizure is where in the brain it starts. That single fact splits seizures into two broad families, and it shapes everything from how the seizure looks to which medicine will work.

Focal seizures begin in one part — one “focus” — of a single hemisphere. The symptoms depend entirely on the job that bit of brain does: a focus in the motor strip causes jerking of one limb; in the visual cortex, flashing lights or shapes; in the temporal lobe, an odd smell, a wave of fear or the eerie sense of having lived a moment before (déjà vu). Focal seizures are sub-divided by whether awareness is kept. In a focal aware seizure (the old term was “simple partial”) the person stays conscious and may describe the experience — this is what used to be called an “aura”, and is really a small seizure in its own right. In a focal impaired awareness seizure (“complex partial”) consciousness is clouded; the person may stare, fumble, smack their lips or wander, with no memory of it afterwards. A focal seizure can spread and become a convulsion — a focal to bilateral tonic-clonic seizure.

Generalised seizures involve networks across both hemispheres from the very start, so consciousness is usually lost immediately. The best known is the tonic-clonic seizure (once called grand mal): the body stiffens (the tonic phase, often with a cry as air is forced out), then jerks rhythmically (the clonic phase), after which the person is drowsy and confused for a while — the “postictal” state. Others are subtler. An absence seizure (petit mal), common in children, is a few seconds of blank staring that can be mistaken for daydreaming. The table below sets out the main types.

What causes epilepsy — and triggers

Epilepsy is not one disease but a symptom shared by many. Modern classification (from the International League Against Epilepsy) sorts the underlying causes into six overlapping groups:

• Genetic — the epilepsy arises directly from a gene variant, often one affecting an ion channel (the tiny protein gates that carry the electrical signal). These need not be inherited; many are new mutations. This is the largest single group.
• Structural — a physical difference in the brain: a stroke, a tumour, scarring from a head injury, a malformation present from birth, or hippocampal sclerosis. Stroke is the commonest cause of new epilepsy in older people.
• Infectious — the result of an infection such as meningitis, encephalitis, or, the leading cause worldwide, neurocysticercosis (a parasitic infection of the brain).
• Metabolic — an inherited problem of the body's chemistry that disturbs how brain cells work.
• Immune — the immune system attacking the brain (autoimmune encephalitis), an increasingly recognised and treatable cause.
• Unknown — in a large share of cases, even after thorough investigation, no cause is found. This is honest medicine, not a failure: the tools are improving every year.

Separately from the underlying cause, many people with epilepsy find that certain things make a seizure more likely on a given day. These are triggers, and knowing your own is a practical part of living well with the condition.

How it's diagnosed

Diagnosing epilepsy is, perhaps surprisingly, still mostly a matter of listening. There is no single test that says yes or no. The most valuable evidence is a careful clinical history: exactly what happened before, during and after the event — and crucially, an eyewitness account, because the person having the seizure often remembers nothing of it. A phone video of an episode, if anyone managed to take one, can be more useful than any scan. The doctor is trying first to establish whether the event was a seizure at all (fainting, migraines, and non-epileptic attacks can mimic one), and then what kind.

Two investigations support the picture. An EEG (electroencephalogram) records the brain's electrical activity through sensors on the scalp; it can catch the tell-tale abnormal discharges between seizures and help classify the epilepsy, though a normal EEG does not rule epilepsy out. An MRI scan looks for a structural cause — a scar, a malformation, a tumour — that might be driving focal seizures and might, in some cases, be removable by surgery. Blood tests, and sometimes a heart tracing, help exclude provoked causes and mimics.

This is also where the seizure-versus-epilepsy distinction matters most. A first seizure is not automatically epilepsy. Around one in ten people will have a seizure at some point in life, but only a fraction go on to develop the recurrent, unprovoked seizures that define the condition. After a first seizure the question is the risk of another, which the history, the EEG and the MRI together help estimate — and that risk guides whether to start treatment now or watch and wait.

A short history

Few conditions have carried so much meaning. For most of recorded history epilepsy was the “sacred disease” — a sign of possession by gods or demons, awe-inspiring and feared in equal measure. The decisive break came around 400 BCE, when the Hippocratic writer of On the Sacred Disease argued, with startling clarity, that epilepsy was no more sacred than any other illness: it arose from the brain, not the gods, and had a natural cause that could one day be understood. It took more than two millennia for medicine to make good on that claim.

In the nineteenth century the English neurologist John Hughlings Jackson watched how focal seizures “marched” across the body — a twitch spreading from a finger up the arm — and reasoned that they must reflect a discharge starting in a specific, localised patch of the cerebral cortex. This insight into cortical localisation helped found modern neurology and still underlies how we map seizures today.

Treatment followed. Bromide, introduced in 1857, was the first drug that genuinely reduced seizures, though at the cost of sedation and toxicity. Phenobarbital arrived in 1912 and phenytoin in 1938 — both still in use — opening the era of targeted anti-seizure medicines. Meanwhile, in the 1920s, the German psychiatrist Hans Berger recorded the first human EEG, giving doctors their first window onto the electrical storms themselves. From the late twentieth century the pace quickened: dozens of new anti-seizure medicines, refined epilepsy surgery, and the imaging that makes it precise. The arc runs from demons to ion channels — one of medicine's clearer victories over superstition.

Treatment

Here is the genuinely encouraging part: epilepsy is, for most people, very treatable. The mainstay is medication, and the headline figure is worth repeating — around two in three people with epilepsy become seizure-free on anti-seizure medicines.

Anti-seizure medications (ASMs) — the older name was anti-epileptic drugs — work by steadying the brain's electrical activity, typically by calming over-excitable neurons or boosting the inhibitory GABA system. The guiding principles are monotherapy (try to control seizures with a single drug at the lowest effective dose, to limit side effects) and matching the drug to the seizure type, since a medicine that suits focal seizures may be wrong, or even worsen, a generalised epilepsy. Finding the right fit can take patience.

When seizures persist despite two well-chosen, well-tolerated medicines tried properly, the epilepsy is called drug-resistant (or refractory), and this affects roughly a third of people. It is the cue to look at other options, ideally at a specialist centre:

• The ketogenic diet — a strict, very high-fat, very low-carbohydrate diet that shifts the body's fuel to ketones — can markedly reduce seizures, especially in children with otherwise hard-to-control epilepsy. It is a real medical treatment, supervised by a dietitian, not a lifestyle fad.
• Epilepsy surgery — when seizures reliably start in one identifiable, safely removable spot (often the temporal lobe), removing or disconnecting that focus can stop seizures altogether. For the right candidate it can be life-changing and even curative.
• Neurostimulation — implanted devices that calm the brain's electrical activity: VNS (vagus nerve stimulation), RNS (responsive neurostimulation, which senses and interrupts seizures as they begin), and DBS (deep brain stimulation). These are options when surgery is not, and they typically reduce rather than abolish seizures.

There is one more option that sometimes surprises people: stopping medication. For someone who has been seizure-free for several years, particularly some childhood epilepsies that are outgrown, a doctor may suggest a slow, supervised withdrawal of medicines. This is always a careful, individual decision — never something to do on your own, since abruptly stopping ASMs can itself trigger seizures.

Living with epilepsy

Most people with epilepsy live full, ordinary lives — work, study, relationships, parenthood, sport. But a few practical matters deserve honest, plain attention.

Driving. Because a seizure at the wheel is dangerous, licensing authorities set rules: in the UK, you must tell the DVLA, and you generally need to have been free of seizures (that affect consciousness) for a defined period — commonly a year — before driving again. The exact rules vary by country and licence type; the point is that they exist for everyone's safety and are not a punishment.

Safety adjustments. Small changes lower the risk of harm if a seizure does happen: showers rather than baths (to avoid drowning), care around open water and heights, never swimming alone, and not locking the bathroom door. The aim is sensible precaution, not a shrunken life.

SUDEP. One subject deserves to be raised gently but honestly, because silence around it does more harm than good. SUDEP — sudden unexpected death in epilepsy — is a rare event in which a person with epilepsy dies suddenly, with no other cause found, usually thought to involve breathing or heart rhythm being disrupted during or after a seizure (often at night). It is rare, and the single most important thing to know is that the strongest protection against it is the same as the goal of treatment generally: good seizure control, particularly of night-time tonic-clonic seizures. Taking medication reliably, getting enough sleep, and not stopping treatment without advice are the practical levers. SUDEP Action offers support and clear information.

Pregnancy and sodium valproate. Epilepsy and pregnancy are entirely compatible — most pregnancies go well — but they need planning, because some seizures and some medicines carry risk. One medicine in particular, sodium valproate, carries a serious warning: taken in pregnancy it significantly raises the risk of birth defects and of developmental problems in the child, and it should not be used in girls or women of childbearing potential unless there is no alternative and strict pregnancy-prevention conditions are met. Anyone affected should discuss this with their specialist — well before trying to conceive — and never stop medication abruptly on their own.

Stigma. Perhaps the heaviest burden of epilepsy is not the seizures but the old fear and misunderstanding around them. Epilepsy is not contagious, not a sign of low intelligence, and not, despite millennia of myth, anything supernatural. Openness — telling colleagues, friends and teachers what a seizure looks like and what to do — turns fear into competent help, and is one of the kindest things a society can learn.

What the research says

Epilepsy is a field moving quickly, and several frontiers are worth watching.

• Genomics and precision treatment. Cheap genetic sequencing is uncovering the specific gene variants behind many epilepsies, and in a growing number of cases the diagnosis now points to a tailored treatment — sometimes a drug that targets the exact faulty channel, and, in early trials, gene therapies aimed at the root cause.
• Better surgical targeting. Advances in imaging, in intracranial recording, and in minimally invasive techniques (such as laser ablation) are making epilepsy surgery safer and available to more people, by pinpointing the seizure focus with growing accuracy.
• Seizure detection and prediction. Wearable devices and smartwatches that sense the movements or physiological changes of a seizure can alert a carer — valuable for night-time convulsions — and researchers are working towards genuine prediction, warning of a seizure before it happens.
• Cannabidiol. A purified cannabidiol medicine (Epidiolex) — a cannabis-derived compound without the “high” — is now an approved, evidence-backed treatment for two severe childhood epilepsies, Dravet syndrome and Lennox-Gastaut syndrome, a notable example of careful trials turning a folk remedy into a real medicine.

Where to get help & more info

If you or someone you know has had a seizure, or is living with epilepsy, you are not on your own, and there are excellent, trustworthy sources of information and support. And to repeat the most important thing on this page: call 999 (UK) or 911 (US) if a seizure lasts more than five minutes, repeats without recovery, is someone's first, involves injury or water, causes breathing trouble, or happens to someone pregnant.

• NHS — Epilepsy — clear, practical UK health-service guidance.
• World Health Organization — Epilepsy fact sheet — the global picture.
• Epilepsy Society (UK) — information, research and support.
• Epilepsy Action (UK) — advice, helpline and local groups.
• Epilepsy Foundation (US) — a deep resource library and support network.
• NINDS (US National Institutes of Health) — the science and the research frontier.
• SUDEP Action (UK) — support and information on sudden unexpected death in epilepsy.
• CDC (US) — public-health information on epilepsy and seizures.

You may also find the companion guides useful: sleep (a major trigger), alcohol (a trigger and a cause of withdrawal seizures), and mental health (anxiety and depression often travel alongside epilepsy).

Some of the figures and details on this page — typical ranges, statistics and the biology — were compiled with the help of AI tools and may contain errors or be out of date. They are shared in good faith for general interest only, and are not medical advice. Nothing here is a substitute for a doctor or a qualified health professional; if you are worried about seizures or epilepsy, please seek professional help. Check claims against primary medical sources before relying on them.