Difference Between Epilepsy and Seizures
A seizure is a single event of abnormal electrical brain activity, while epilepsy is a chronic disorder defined by recurrent unprovoked seizures—specifically, at least two unprovoked seizures occurring more than 24 hours apart, one unprovoked seizure with high recurrence risk (≥60% over 10 years), or diagnosis of an epilepsy syndrome. 1, 2, 3
Core Distinction
Seizures are symptoms, not diseases. They represent transient episodes of abnormal excessive or synchronous neuronal activity in the brain that cause clinical manifestations such as movements, altered consciousness, or sensory changes. 1, 4 Approximately 10% of the population will experience at least one seizure during their lifetime, but this does not mean they have epilepsy. 1, 4
Epilepsy, in contrast, is a chronic neurological disorder characterized by an enduring predisposition to generate recurrent seizures. 5, 3 It affects approximately 1-3% of the U.S. population (3.4 million people) and 50-65 million people worldwide. 1, 4
Critical Classification Framework
Provoked vs. Unprovoked Seizures
The distinction between provoked and unprovoked seizures is fundamental to understanding whether a patient has epilepsy:
Provoked (acute symptomatic) seizures occur at the time of or within 7 days of an acute insult and do NOT constitute epilepsy. 6, 2 Common triggers include:
- Electrolyte abnormalities (hyponatremia, hypocalcemia, hypomagnesemia) 6
- Metabolic derangements (hypoglycemia, hyperglycemia, uremia) 6
- Toxic ingestions (cocaine, tricyclic antidepressants, theophylline) 6
- Alcohol withdrawal 6
- Acute CNS infections (meningitis, encephalitis) 6
- Acute stroke or traumatic brain injury 6
Unprovoked seizures occur without acute precipitating factors and may indicate epilepsy, particularly if recurrent. 6, 2 These include:
- Remote symptomatic seizures (from prior stroke >7 days old, remote TBI, cortical malformations) 6
- Idiopathic seizures (no identifiable cause) 6
- Genetic epilepsy syndromes 6
When Does a Seizure Become Epilepsy?
The International League Against Epilepsy (ILAE) defines epilepsy as meeting ANY of these three criteria: 1, 3
- At least two unprovoked seizures occurring more than 24 hours apart 1, 3
- One unprovoked seizure with a probability of recurrence ≥60% over the next 10 years (similar to the risk after two unprovoked seizures) 1, 3
- Diagnosis of an epilepsy syndrome (specific patterns with characteristic features including seizure type, age of onset, EEG findings, and neuroimaging) 1, 3
High-Risk Features for Recurrence
After a single unprovoked seizure, the following features indicate ≥60% recurrence risk and may warrant an epilepsy diagnosis: 2
- History of prior brain insult 2
- Epileptiform abnormalities on EEG 2
- Structural lesion on neuroimaging 2
Treatment Implications
This distinction has profound treatment implications:
For provoked seizures: Treat the underlying cause rather than initiating long-term antiseizure medications. 2 Antiepileptic drugs (AEDs) are NOT indicated for provoked seizures. 4
For epilepsy (recurrent unprovoked seizures): AED therapy is the standard treatment, with medication selection depending on seizure type, epilepsy syndrome, comorbidities, and drug characteristics. 2, 4
Common Pitfall
The most critical error is falsely diagnosing epilepsy when a patient has only experienced provoked seizures or non-epileptic events. When uncertain about the diagnosis, it is better to postpone labeling someone with epilepsy than to falsely diagnose it, given the significant psychosocial, treatment, and quality-of-life implications. 2 Approximately 8% of seizure patients have correctable metabolic abnormalities that, once treated, eliminate the seizure risk without requiring chronic epilepsy management. 2
Epilepsy can be considered resolved in individuals who have remained seizure-free for the last 10 years and off antiseizure medicines for at least the last 5 years, or who had an age-dependent epilepsy syndrome and are now past the applicable age. 3