What is Epilepsy
Epilepsy is a brain disease defined by having at least two unprovoked seizures occurring more than 24 hours apart, one unprovoked seizure with ≥60% probability of recurrence over the next 10 years, or diagnosis of an epilepsy syndrome. 1, 2, 3
Core Definition
The International League Against Epilepsy (ILAE) established this practical definition in 2014, expanding beyond the traditional "two unprovoked seizures" criterion to allow earlier diagnosis and treatment initiation when recurrence risk is high. 3, 4
- An epileptic seizure is a transient occurrence of signs and/or symptoms caused by excessive, abnormal, or synchronous neuronal activity in the brain. 1
- Unprovoked seizures occur without acute precipitating factors (such as electrolyte abnormalities, alcohol withdrawal, or acute brain injury) and indicate an enduring predisposition to generate seizures. 5, 2
- Provoked seizures occur at the time of or within 7 days of an acute neurologic, systemic, metabolic, or toxic insult and do not constitute epilepsy. 5
When Epilepsy is Considered Resolved
Epilepsy can be considered resolved (not necessarily cured) under two circumstances: 3, 4
- Individuals who had an age-dependent epilepsy syndrome but are now past the applicable age
- Those who have remained seizure-free for the last 10 years AND off antiseizure medications for at least the last 5 years 3, 4
Epidemiology and Impact
- Approximately 10% of the population will experience at least one seizure during their lifetime, but this does not mean they have epilepsy. 1
- Active epilepsy affects approximately 1.2% of the US population (3.4 million people) and 50 million people worldwide. 1
- The condition has significant impact on mortality, morbidity, and quality of life. 1
Classification Framework
Epilepsy is classified along multiple dimensions: 1, 5
By Seizure Type:
- Focal onset seizures arise within networks of a single cerebral hemisphere and may remain localized or spread more widely 1, 5
- Generalized onset seizures rapidly affect both hemispheres and both sides of the body from onset 1, 5
- Unknown onset seizures when the origin cannot be determined 1
By Epilepsy Type:
- Focal epilepsy
- Generalized epilepsy
- Combined focal and generalized epilepsy
- Unknown epilepsy 1
By Etiology:
- Structural (hippocampal sclerosis, tumor, focal cortical dysplasia, hemorrhage)
- Genetic
- Infectious
- Metabolic
- Immune
- Unknown 1
Multiple etiologic categories can coexist in the same patient. 1
Critical Diagnostic Principle
When uncertain about the diagnosis, it is better to postpone the diagnosis than to falsely diagnose epilepsy, given the significant treatment and psychosocial implications. 1 A single seizure does not automatically constitute epilepsy unless there is documented high recurrence risk (≥60% over 10 years). 2, 3