What Is Epilepsy vs a Seizure

This article is educational and is not medical advice. It does not diagnose, treat, prevent, or cure any condition. Komori is not a medical device, is not FDA-cleared, does not detect seizures, and is not intended for people with epilepsy. Talk with a neurologist or epileptologist about personal medical decisions. Households living with epilepsy should use clinically validated seizure-detection devices as directed by their care team.

People mash "seizure" and "epilepsy" together like they mean the same thing. They don't.

A seizure is an event. Epilepsy is a diagnosis. You can have one without the other. I'm not a neurologist. I don't have epilepsy. I read the CDC, NINDS, and ILAE papers so the words here match what a clinician actually uses.

A seizure is short. That's the job description.

The International League Against Epilepsy still uses the 2005 conceptual line, restated in its 2014 clinical paper. An epileptic seizure is a transient occurrence of signs or symptoms caused by abnormal excessive or synchronous neuronal activity in the brain.

Plain English: a bunch of neurons fire together in a way they shouldn't. Then it stops.

CDC's public version is shorter. A seizure is a change in normal brain activity that lasts from a few seconds to a few minutes.

NINDS fills in the texture. During a seizure, many neurons send signals at the same time, much faster than normal. That surge can cause movements, sensations, emotions, or behaviors the person did not choose. It can also knock out awareness.

TV almost always shows a person hitting the floor and shaking. CDC is blunt about that picture. That's one kind of seizure. It's not the most common.

More often, someone stares, looks confused, wanders, makes odd movements, or can't answer a simple question. A seizure is still a seizure if nobody falls down.

Epilepsy is the tendency, not the single event

CDC's public definition: epilepsy is a brain disorder that causes repeated seizures.

NINDS calls it a chronic brain disorder in which groups of neurons sometimes send the wrong signals. They also use "the epilepsies," plural, because types and causes vary so much that one word barely covers it.

The definition a neurologist actually applies is the ILAE 2014 practical one. Epilepsy is a disease of the brain if any one of these is true:

1. At least two unprovoked (or reflex) seizures more than 24 hours apart.
2. One unprovoked (or reflex) seizure plus a probability of further seizures similar to the recurrence risk after two unprovoked seizures, at least 60 percent, over the next 10 years.
3. Diagnosis of an epilepsy syndrome.

NINDS still teaches the everyday version: epilepsy is generally diagnosed after two or more unprovoked seizures separated by at least 24 hours. The 2014 paper kept that rule and added paths clinicians were already using.

A diagnosis of epilepsy is not the same as a decision to start medicine. ILAE says that out loud. Those are clinician calls.

Epilepsy is also not automatically lifelong. ILAE considers it resolved if the person had an age-dependent syndrome and is now past that age, or if they have been seizure-free for the last 10 years and off antiseizure medicines for at least the last 5 years. "Resolved" is not "cured." The paper is picky about that word for a reason.

Unprovoked vs provoked is the fork in the road

This is the distinction that decides whether a first seizure even counts toward epilepsy.

A provoked seizure (also called an acute symptomatic seizure) happens when a temporary factor acting on an otherwise normal brain lowers the threshold. ILAE's 2014 examples: a seizure after a concussion, with fever, or during alcohol withdrawal. NINDS adds extreme blood sugar, sudden changes in blood chemicals, eclampsia, and kidney or liver failure.

An unprovoked seizure happens without that kind of immediate, reversible trigger.

A brain tumor can cause a seizure without being a transient insult. That event can still count as unprovoked. Reflex seizures, like those triggered by flashing lights, still count toward epilepsy if the person has an enduring tendency to seize in response to that stimulus.

ILAE calls the border imprecise. Only a clinician can put a given event on one side or the other. Triggers in someone who already has epilepsy, like missed sleep or stress, are not the same thing as the cause of epilepsy.

One seizure is not automatically epilepsy

NINDS is direct. Having a seizure does not by itself mean a person has epilepsy.

First seizures, febrile seizures in children, nonepileptic events, and eclampsia can involve seizures or seizure-like episodes and still not be epilepsy.

CDC first-aid guidance adds a population fact I wish more people knew. About 1 in 10 people in the United States may have a seizure in their lifetime. Most of those people will never meet criteria for epilepsy.

The American Academy of Neurology and the American Epilepsy Society put numbers on what happens after a first unprovoked seizure in adults. The chance of another is greatest in the first two years, in the 21 to 45 percent range. A prior brain insult (stroke, trauma) and an EEG with epileptiform abnormalities raise that risk. ILAE 2014 cites older work putting recurrence after one unprovoked seizure in the 40 to 52 percent range. The 60 percent path is for clinicians who already know the risk is that high. It is not a DIY calculator.

How common this actually is

CDC estimates about 2.9 million U.S. adults had active epilepsy in 2021, and about 456,000 U.S. children age 17 or younger in 2022. Less than half of newly diagnosed cases have a known cause. When a cause is found, CDC lists cysticercosis as the leading cause worldwide, then stroke, brain tumor, traumatic brain injury, and genetic conditions. Epilepsy is not contagious.

Diagnosis is a clinician's job

No article, including this one, can diagnose epilepsy.

NINDS describes the actual work. A detailed history still matters most, including what the person felt beforehand and what witnesses saw. Tests that may follow include EEG, MRI or CT, blood work, and sometimes video-EEG. Those tools help a neurologist. They do not turn a blog post into a diagnosis.

ILAE 2014 is equally cautious. A single seizure plus an MRI lesion, or a single seizure plus EEG spikes, does not automatically meet criterion 2. When the risk is unclear, the default remains two unprovoked seizures more than 24 hours apart.

FAQ

What is the difference between a seizure and epilepsy?

A seizure is a short change in brain activity. Epilepsy is a diagnosis of an enduring tendency to have epileptic seizures, using CDC language and the ILAE 2014 criteria.

Does one seizure mean I have epilepsy?

No. NINDS states that having a seizure does not by itself mean a person has epilepsy. Diagnosis is a clinician's decision.

What is an unprovoked seizure?

An unprovoked seizure occurs without a temporary, reversible factor that lowered the seizure threshold at that moment. A provoked seizure is tied to an immediate insult, such as fever or acute head injury. ILAE notes that this border can be imprecise.

Can epilepsy go away?

ILAE 2014 allows epilepsy to be called resolved after an age-dependent syndrome once the person is past the relevant age, or after 10 years seizure-free with at least the last 5 years off antiseizure medicine. Resolved is not the same as cured.

Sources

• CDC, Epilepsy Basics: https://www.cdc.gov/epilepsy/about/index.html
• CDC, First Aid for Seizures: https://www.cdc.gov/epilepsy/first-aid-for-seizures/index.html
• NINDS, Epilepsy and Seizures: https://www.ninds.nih.gov/health-information/disorders/epilepsy-and-seizures
• Fisher et al., ILAE Official Report: A practical clinical definition of epilepsy, Epilepsia (2014): https://www.ilae.org/files/ilaeGuideline/Definition2014.pdf
• AAN/AES, Management of an Unprovoked First Seizure in Adults: https://www.aan.com/Guidelines/Home/GetGuidelineContent/688

Related reading: Types of seizures and seizure first aid.