What Is Epilepsy? – Epilepsy: The Untold Side

Epilepsy is a disease of the brain characterised by an enduring predisposition to have epileptic seizures. It is not one single condition, and it is not defined by convulsions alone.

An epileptic seizure is a temporary occurrence of signs or symptoms caused by abnormal excessive or synchronous neuronal activity in the brain. Depending on the networks involved, a seizure may cause convulsions, but it may also cause a brief pause, altered consciousness, unusual sensations, changes in memory or emotion, muscle jerks, stiffening, falls, automatic behaviour or symptoms that nobody else can see.

The formal clinical definition of epilepsy

The International League Against Epilepsy (ILAE) practical clinical definition allows epilepsy to be diagnosed when any one of the following applies:

At least two unprovoked or reflex seizures occurring more than 24 hours apart.
One unprovoked or reflex seizure and a probability of further seizures similar to the general recurrence risk after two unprovoked seizures — approximately 60% or more over the next 10 years.
Diagnosis of an epilepsy syndrome.

This means the often-repeated statement that someone must have “two seizures before it can be epilepsy” is not always correct. In some circumstances, one seizure plus strong evidence of an enduring high risk of recurrence can meet the definition.

One seizure does not automatically mean epilepsy

A seizure can occur because of an acute, temporary disturbance affecting the brain. Examples include severe hypoglycaemia, major electrolyte disturbance, acute infection affecting the brain, alcohol withdrawal, certain drug-related states or an acute brain injury. These are often described clinically as acute symptomatic or provoked seizures.

A seizure caused only by a temporary provoking factor does not, by itself, establish epilepsy. Epilepsy implies an enduring predisposition to generate epileptic seizures rather than a one-off response to a short-lived disturbance.

The distinction can be complicated. For example, a seizure during an acute stroke is different from recurrent unprovoked seizures caused by a lasting structural brain change after a previous stroke. The underlying context matters.

What about seizure triggers?

A trigger is not necessarily the same thing as an acute provoking cause. Someone who already has epilepsy may be more likely to have a seizure after sleep deprivation, missed medication, illness, stress or alcohol exposure. The presence of a trigger does not automatically make that seizure non-epileptic or mean the person does not have epilepsy.

This is an important distinction: a person with an enduring epileptic predisposition can still have seizures that are made more likely by particular circumstances.

Reflex seizures

Some epileptic seizures are consistently triggered by a specific stimulus or activity. These are called reflex seizures. Examples can include visually induced seizures in susceptible people, or much rarer seizures associated with particular cognitive, sensory or motor activities.

Because the underlying brain has an enduring predisposition to respond with epileptic seizures, reflex seizures can form part of epilepsy even though an identifiable stimulus is present.

Epilepsy is not simply “abnormal electrical activity”

It is common to describe epilepsy as abnormal electrical activity in the brain, which is useful as a simple explanation, but the biology is more complex. Epileptic seizures arise from abnormal activity within neuronal networks. Different networks can produce very different seizure manifestations, and epilepsy can involve structural, genetic, infectious, metabolic, immune and currently unknown causes.

This network-based view helps explain why two people can both have epilepsy yet have completely different seizures, EEG findings, MRI results, treatment responses and day-to-day effects.

Seizure type, epilepsy type and epilepsy syndrome are different

A seizure type describes an individual seizure. An epilepsy type describes the broader pattern of the epilepsy. An epilepsy syndrome is a recognisable clinical pattern that can include characteristic seizure types, age of onset, EEG findings, imaging, genetics, developmental features and prognosis.

A person can have more than one seizure type. The diagnosis may also become more specific over time as EEG, MRI, genetic testing, clinical history or further seizures provide additional information.

Read more: Seizure Types →

The main epilepsy types

At the epilepsy level, clinicians consider whether the pattern is predominantly focal, generalised, a combination of generalised and focal features, or whether the type remains unknown. This is separate from classifying an individual seizure.

Correct classification matters because it can influence which investigations are useful, which epilepsy syndrome is considered and which antiseizure medicines are most appropriate.

What causes epilepsy?

Epilepsy does not have one cause. Modern classification considers several broad aetiological groups, and more than one may apply to the same person.

Structural: a visible or presumed brain abnormality associated with increased seizure risk, such as hippocampal sclerosis, focal cortical dysplasia, previous stroke, brain injury or a tumour.
Genetic: epilepsy resulting directly from a known or presumed genetic variation. “Genetic” does not necessarily mean inherited from a parent; some variants arise for the first time in the affected person.
Infectious: epilepsy resulting from infection-related brain disease.
Metabolic: epilepsy caused by a specific metabolic disorder.
Immune: epilepsy resulting from an immune-mediated process affecting the brain.
Unknown: the cause cannot currently be identified.

Finding no cause does not mean the epilepsy is not real. Sometimes the underlying mechanism is simply beyond what current tests can detect.

Read more: Genetics & Epilepsy →

Epilepsy can exist even when tests are normal

There is no single test that proves or excludes epilepsy in every person. A routine EEG may be normal between seizures, and an MRI may show no structural abnormality. Diagnosis comes from combining the clinical history with examination and appropriate investigations.

Conversely, an abnormal EEG or scan does not automatically prove that every unexplained event is an epileptic seizure. Test findings must fit the clinical picture.

Read more: Diagnosis and Tests →

Epilepsy is more than the seizure itself

The ILAE conceptual definition recognises not only an enduring predisposition to seizures but also the possible neurobiological, cognitive, psychological and social consequences of the condition.

For some people, the seizure is only a small part of the overall burden. Epilepsy may also involve memory and concentration problems, injuries, post-seizure confusion, exhaustion, medication adverse effects, anxiety, depression, disrupted sleep, restrictions on driving or employment, relationship pressures, stigma and uncertainty about when another seizure may occur.

That wider reality is central to Epilepsy: The Untold Side: understanding what happens before, after and between seizures, not only what other people can see during one.

Can epilepsy go into remission?

Yes. Some people become seizure-free for long periods, either with treatment or after medication is eventually withdrawn under specialist guidance. Some age-dependent epilepsy syndromes also remit as a person grows older.

Seizure freedom does not automatically mean that epilepsy has disappeared permanently, and decisions about reducing or stopping antiseizure medication require individual assessment of recurrence risk.

What does “resolved epilepsy” mean?

The ILAE uses the term resolved in specific circumstances. Epilepsy may be considered resolved when a person had an age-dependent epilepsy syndrome but is now past the applicable age, or when the person has been seizure-free for at least 10 years and has taken no antiseizure medication for at least the most recent 5 years.

“Resolved” does not necessarily mean that there is zero lifetime risk of another seizure, and the ILAE deliberately distinguishes it from claiming that epilepsy has been permanently cured.

Epilepsy is not the same as every episode that looks like a seizure

Syncope, cardiac rhythm disorders, migraine, sleep disorders, movement disorders and functional or dissociative seizures can sometimes resemble epileptic seizures. Some people can also have both epilepsy and another type of episodic event.

That is why careful diagnosis matters and why appearance alone — including whether somebody shakes — cannot establish the diagnosis.

How common is epilepsy?

Epilepsy is one of the most common neurological diseases worldwide and affects people of all ages and backgrounds. The World Health Organization estimates that around 50 million people worldwide live with epilepsy.

The central point

Epilepsy is not simply “having fits”. It is a group of brain diseases characterised by an enduring predisposition to epileptic seizures, with many possible seizure types, causes and consequences. Some seizures are dramatic; others are almost invisible. Some people become seizure-free; others live with persistent seizures despite treatment.

Understanding epilepsy properly means looking beyond the visible seizure to the brain networks involved, the underlying cause, the likelihood of recurrence, the epilepsy type or syndrome, and the impact on the person’s life.

Where next?

Seizure Types →
Diagnosis and Tests →
Treatment Options →
Genetics & Epilepsy →
Back to Understanding Epilepsy →

Sources

Medical note: This page is for education and awareness and is not a substitute for individual medical advice. Diagnosis, classification and treatment should be based on a person’s individual clinical circumstances.

Evidence checked: September 2026.