UNDERSTANDING EPILEPSY
Epilepsy is not one condition, one seizure type, or one experience.
It is a neurological condition characterised by an enduring tendency to have epileptic seizures, but what that looks like can vary greatly from one person to another.
Some seizures are obvious. Others may look like staring, confusion, unusual movements, brief loss of awareness, changes in sensation, sudden drops, or experiences that are difficult to describe from the outside.
This page is here to make epilepsy easier to understand without reducing it to a single picture.
We’ll explore:
what epilepsy is
different seizure types
diagnosis and testing
treatment and medication
triggers and seizure risk
recovery after seizures
memory, thinking and everyday life
safety and support
terminology and common misconceptions
the science of epilepsy
the history of epilepsy
how epilepsy has been understood across different cultures and periods of time
how research and treatment have changed
the social impact of epilepsy, including stigma and discrimination
The aim is not to tell people what their epilepsy should look like. It is to explain how broad epilepsy can be.
WHAT IS EPILEPSY?
Epilepsy is a neurological disease characterised by an enduring tendency to have epileptic seizures.
An epileptic seizure is a temporary occurrence of signs or symptoms caused by abnormal excessive or highly synchronous activity in the brain.
Epilepsy is not one single condition and seizures do not all look the same.
Depending on where and how seizure activity occurs, a seizure may affect things such as:
awareness
movement
sensation
thinking or memory
emotions
behaviour
speech or communication
responsiveness
Some seizures are obvious to an observer. Others can be subtle and may be difficult to recognise from the outside.
Having one seizure does not automatically mean someone has epilepsy. The ILAE's practical definition allows epilepsy to be diagnosed in several circumstances, including two unprovoked seizures more than 24 hours apart, or one unprovoked seizure where there is a sufficiently high risk of further seizures.
Epilepsy can also be classified further by seizure type, epilepsy type, syndrome and cause.
Epilepsy describes a disease of the brain. It does not describe one seizure type, one appearance, or one person's experience.
One other important thing for this website: the ILAE released an updated seizure classification in 2025, so when we get to seizure types I want us to use that rather than building the page around the older 2017 terminology.
WHAT IS A SEIZURE
An epileptic seizure is a temporary event caused by abnormal excessive or highly synchronous activity in the brain.
What happens during a seizure depends on which brain networks are involved and how the activity develops.
A seizure may begin in one part of the brain, involve both sides from the start, or have an onset that cannot initially be determined.
Some seizures are obvious to an observer. Others can be subtle or difficult to recognise from the outside.
Modern seizure classification therefore looks not only at what a seizure looks like, but also at where it begins and which features occur during it.
There is no single appearance that defines an epileptic seizure.
HOW ARE SEIZURES CLASSIFIED?
The International League Against Epilepsy (ILAE) updated its seizure classification in 2025 to give clinicians, researchers and people affected by epilepsy a clearer common language.
The current system has four main seizure classes:
Focal
Generalised
Unknown whether focal or generalised
Unclassified
The updated system also separates classifiers from descriptors.
Classifiers help place a seizure into its main biological category and can affect diagnosis and treatment decisions.
Descriptors explain what happens during the seizure — for example, whether there are observable movements, speech changes, autonomic features, or other signs.
For focal seizures, the 2025 system uses consciousness as a classifier, described as either preserved or impaired. Consciousness is assessed using both awareness and responsiveness.
Another major change is that seizures are now described by the sequence of signs and symptoms as they develop, rather than relying only on the first feature seen. The older motor/non-motor split has also been replaced by whether manifestations are observable or non-observable.
The 2025 classification contains 21 seizure types, compared with 63 in the 2017 system. It also formally recognises epileptic negative myoclonus as a seizure type.
Classification is a way of describing seizures more precisely — it is not a measure of how serious or important one person’s epilepsy is compared with another’s.
FOCAL SEIZURES
Focal seizures begin within networks limited to one hemisphere of the brain. They may start in a small, localised area or involve a wider network within that hemisphere.
Under the ILAE 2025 classification, focal seizures can be classified as:
Focal preserved consciousness seizure
Focal impaired consciousness seizure
Focal to bilateral tonic–clonic seizure
If consciousness cannot be determined, the seizure can remain classified simply as a focal seizure.
In the 2025 system, consciousness is assessed using both awareness and responsiveness.
A person may therefore have their eyes open or appear to interact during a seizure and still have impaired consciousness if awareness or responsiveness is affected.
Focal seizures can have many different features depending on the brain networks involved. They may include sensory experiences, autonomic changes, speech or language changes, automatisms, stiffening, jerking, unusual movements or other observable and non-observable features.
The ILAE now encourages these features to be described in the order they happen, rather than defining the seizure only by its first sign.
A focal to bilateral tonic–clonic seizure begins as a focal seizure and then spreads to involve both hemispheres, progressing to loss of consciousness, bilateral stiffening and then a clonic phase.
Focal does not mean minor. It describes where the seizure begins, not how much it affects the person.
GENERALISED SEIZURES
Generalised seizures are defined by the ILAE as seizures that begin at some point within, and rapidly engage, networks distributed across both sides of the brain. These networks may involve cortical and subcortical structures, but they do not necessarily involve the entire cortex.
A generalised seizure can sometimes look asymmetric or appear to have a more localised beginning, so appearance alone does not always tell you where the seizure started.
Under the 2025 ILAE system, generalised seizures include several seizure types, such as:
generalised tonic–clonic seizures
absence seizures
myoclonic seizures
tonic seizures
clonic seizures
atonic seizures
epileptic spasms
epileptic negative myoclonus
The exact features depend on the seizure type and the brain networks involved. Some generalised seizures involve obvious movement, while others may mainly affect consciousness, responsiveness or other functions.
One important point is that generalised does not mean “more severe” than focal. It describes the pattern of brain-network involvement used for classification.
Generalised seizures are defined by how seizure activity engages the brain, not simply by how dramatic the seizure looks.
WHEN IT ISN’T CLEAR WHETHER A SEIZURE IS FOCAL OR GENERALISED
Not every epileptic seizure can be classified immediately as focal or generalised.
Under the ILAE 2025 system, “unknown whether focal or generalised” is used when there is some information about the seizure, but not enough to determine confidently whether it belongs to the focal or generalised class.
This can happen when:
the beginning of the seizure was not seen
the available history is incomplete
the seizure has features that could fit more than one class
testing has not yet provided enough information
The 2025 classification also keeps a separate category called “unclassified.”
A seizure is considered unclassified when a clinician is confident that the event is an epileptic seizure, but there is not enough information available to place it into one of the other main classes.
These categories are not necessarily permanent. If more information later becomes available — for example from witness accounts, video, EEG findings or further assessment — the seizure may be reclassified more specifically.
“Unknown” or “unclassified” does not mean the seizure is less real. It means there is not yet enough information to describe it more precisely.
WHAT CAUSES EPILEPSY?
There is no single cause of epilepsy.
The International League Against Epilepsy groups the causes of epilepsy into six broad categories: structural, genetic, infectious, metabolic, immune and unknown. A person can sometimes fit into more than one category.
Structural
Epilepsy may be linked to a structural change in the brain. This can include changes caused by stroke, head injury, infection, developmental abnormalities or other brain lesions.
Genetic
Some epilepsies are associated with genetic changes. This does not always mean the condition was inherited directly from a parent; some genetic changes can occur for the first time in an individual.
Infectious
Certain infections affecting the brain can lead to epilepsy.
Metabolic
Some metabolic disorders can disrupt normal brain function and cause epilepsy.
Immune
In some people, epilepsy is associated with an abnormal immune response affecting the brain.
Unknown
For many people, no definite cause is found, even after investigation. The NHS also notes that epilepsy is often related to genetic factors or brain damage, but that in many cases the cause remains unclear.
Finding a cause can matter because it may influence treatment, prognosis, genetic counselling or whether other options such as epilepsy surgery are considered.
Not knowing the cause does not make the epilepsy less real. It simply means the underlying cause has not been identified.
HOW IS EPILEPSY DIAGNOSED?
There is no single test that can diagnose epilepsy on its own.
Diagnosis usually combines what happened during the suspected seizure, the person’s medical history, witness information and the results of investigations. The NHS specifically notes that it can help to bring someone who saw the event, because what happened before, during and after the seizure can be important.
Tests may include:
EEG — records electrical activity in the brain and may help support a diagnosis or identify seizure patterns
MRI — looks for structural changes in the brain that may help explain the epilepsy
CT — may be used when MRI is unsuitable or in particular circumstances
ECG — checks the heart, because some heart problems can cause episodes that resemble seizures
blood tests
genetic testing in selected cases
NICE recommends MRI for most people diagnosed with epilepsy, with specific exceptions such as idiopathic generalised epilepsy and self-limited epilepsy with centrotemporal spikes.
An important point is that a normal EEG does not rule out epilepsy. EEG records brain activity only during the period being measured, and some people with epilepsy will not show characteristic abnormalities on a routine recording. NICE explicitly advises that EEG should not be used to exclude the diagnosis.
If more information is needed, different EEG techniques can be used, including sleep EEG, sleep-deprived EEG, ambulatory EEG and video telemetry, where EEG is recorded alongside video over a longer period.
Epilepsy is diagnosed from the whole clinical picture — not from one scan, one EEG or one symptom.
WHAT DOES AN EEG ACTUALLY SHOW?
An EEG, or electroencephalogram, records the brain’s electrical activity using electrodes placed on the scalp. It can help support a diagnosis of epilepsy and may provide information about seizure type or epilepsy syndrome.
But an EEG has limits.
A normal EEG does not rule out epilepsy. NICE specifically advises that EEG should not be used to exclude the diagnosis because many people with epilepsy will not show epileptiform abnormalities during a routine recording.
If a routine EEG does not provide enough information, other types may be considered, including:
sleep EEG
sleep-deprived EEG
ambulatory EEG, recorded over a longer period while someone goes about everyday activities
video telemetry EEG, where EEG is recorded alongside video, often over several days in hospital
During some routine EEGs, techniques such as hyperventilation or flashing lights may be used, with the person’s agreement, to increase the chance of revealing characteristic changes in brain activity.
An EEG can be valuable, but it is only one part of the picture.
A diagnosis of epilepsy is not determined by whether one EEG is “normal” or “abnormal”. Clinical history, witnessed events and other investigations still matter.
WHAT CAN MRI SHOW IN EPILEPSY?
MRI, or magnetic resonance imaging, creates detailed images of the structure of the brain.
In epilepsy, MRI is used mainly to look for structural abnormalities that may help explain why seizures are occurring. The ILAE describes MRI as a fundamental tool in epilepsy care because it can identify lesions and other structural changes that may be linked to seizures.
Examples of structural causes that may be seen on MRI include:
focal cortical dysplasia
hippocampal sclerosis
vascular malformations
previous stroke or hypoxic brain injury
traumatic brain injury
certain brain tumours
other malformations of brain development
MRI does not show the electrical activity of a seizure in the way an EEG does. Instead, it looks for structural clues that may help explain where seizures are coming from or what may be causing them.
Special epilepsy MRI protocols can make a significant difference. The ILAE recommends dedicated epilepsy imaging sequences, including the HARNESS-MRI protocol, designed to improve the detection of subtle abnormalities that might be missed on a more general brain scan.
A normal MRI does not mean someone does not have epilepsy. Some people have epilepsy without any structural abnormality that can be seen on routine imaging, and some lesions can be subtle enough to require specialist review or advanced imaging techniques.
In people being assessed for epilepsy surgery, imaging can become even more detailed. Depending on the case, this may include techniques such as functional MRI, PET, SPECT or advanced image post-processing alongside EEG and other investigations.
MRI looks for structure. EEG looks at electrical activity. They answer different questions, and both can be important.
HOW IS EPILEPSY TREATED?
Treatment is individual. There is no single treatment that is right for every person with epilepsy.
For most people, anti-seizure medication is the first-line treatment and remains the mainstay of epilepsy management. The medicine chosen depends on factors such as seizure type, epilepsy type or syndrome, age, other health conditions, potential side effects and, where relevant, pregnancy considerations.
Some people become seizure-free with their first medicine. Others may need to try a different medicine or a combination of medicines before finding an approach that works well for them. Treatment should be reviewed with a specialist rather than stopped or changed suddenly without medical advice.
If seizures continue despite appropriate medication, other treatments may be considered. These can include:
epilepsy surgery
vagus nerve stimulation (VNS)
other forms of neurostimulation
a ketogenic diet in selected cases
emergency or rescue medicines for prolonged seizures or seizure clusters
Epilepsy surgery is particularly important for some people with drug-resistant epilepsy, especially when seizures arise from a brain area that can potentially be treated surgically. The ILAE notes that surgery can help some people whose seizures have not responded to medicines.
Treatment is not only about reducing seizure numbers. Clinicians may also need to consider side effects, injuries, mental health, memory and cognition, sleep, independence, quality of life and other conditions occurring alongside epilepsy.
The best treatment plan is the one built around the individual — their epilepsy, their risks, their priorities and their life.
HOW DO ANTI-SEIZURE MEDICINES WORK?
Anti-seizure medicines are the main treatment for epilepsy.
They do not cure epilepsy, but they can reduce the likelihood of seizures by changing how electrical and chemical signalling works in the brain. Different medicines act in different ways, which is one reason why one drug may work well for one person but not another.
The choice of medicine depends on several factors, including:
seizure type
epilepsy type or syndrome
age
other medical conditions
other medicines being taken
possible side effects
pregnancy or the possibility of pregnancy
how the medicine fits into the person’s daily life
NICE recommends choosing treatment according to the individual’s epilepsy and circumstances rather than using one medicine for everyone.
Some people become seizure-free with the first medicine they try. Others may need a different medicine, a combination of medicines, or further specialist assessment if seizures continue.
Side effects vary between medicines and between people. They can include things such as tiredness, dizziness, problems with concentration, mood changes, changes in weight or other effects depending on the specific drug. Any concerns should be discussed with the prescribing clinician.
It is important not to stop anti-seizure medication suddenly unless a clinician has specifically advised it. Abrupt withdrawal can increase the risk of seizures and, in some circumstances, more serious seizure complications.
The aim is not simply to prescribe a medicine. It is to find the best balance between seizure control, side effects and quality of life for that individual.