Epilepsy encompasses a diverse group of disorders characterized by recurrent unprovoked seizures and requires careful evaluation to classify seizure type, identify underlying etiology, and distinguish epileptic events from common mimicking conditions. The International League Against Epilepsy classification provides a standardized framework that separates seizures into focal, generalized, or unknown classes, improving diagnostic consistency across care settings. Accurate identification is essential because misdiagnosis can lead to unnecessary treatment, inappropriate restrictions, and delayed care for the true underlying condition. The most common seizure mimics are syncope, psychogenic nonepileptic attacks (functional neurologic disorder), migraine with aura, transient ischemic attack, movement disorders, metabolic disturbances, and sleep disorders. Epidemiologic studies indicate that epilepsy affects 5 to 9 per 1,000 people in high-income countries, with a higher incidence in older adults due to cerebrovascular disease, dementia and neurodegeneration, and metabolic or systemic disorders. Morbidity and mortality remain significant, with increased risk attributable to status epilepticus, sudden unexpected death in epilepsy, injuries, drowning, and comorbid medical conditions. Understanding of seizure classification, mimic differentiation, and long-term prognosis allows clinicians to provide accurate counseling, initiate appropriate workup, and facilitate specialist referral when needed.
Mullur K, Burbank K. Seizure Disorders in Adults: Understanding the Types of Epilepsy and Nonepileptic Events. FP Essent. 2026;568:12-17.
Case 2. EL is a 20-year-old college student who awoke on his dormitory room floor with a bitten tongue and urinary incontinence. He has no recollection of the event. His roommate reports that EL was confused and fatigued but gradually regained orientation over several minutes. EL experienced one febrile seizure in infancy but has otherwise been healthy. He reports no alcohol or drug use and takes no medications. You perform a neurologic examination, which is normal. He and his mother ask what evaluation is needed, what types of seizures could cause such an episode, and whether he has epilepsy.
Defining Epilepsy and Its Epidemiology
The International League Against Epilepsy (ILAE) defines epilepsy as any of the following clinical criteria: (1) at least two unprovoked seizures occurring more than 24 hours apart; (2) one unprovoked seizure with a probability of further seizures similar to the general recurrence risk after two unprovoked seizures (at least 60% over 10 years based on the presence of high-risk features); or (3) diagnosis of an epilepsy syndrome.1 This definition emphasizes that epilepsy is not only the occurrence of seizures but reflects an enduring predisposition to generate them.
Globally, epilepsy affects approximately 50 million people, with an estimated prevalence in high-income countries of 5 to 9 per 1,000 people and an incidence of 50 to 60 per 100,000 person-years.2 A substantial portion of new diagnoses are in adults, particularly older adults, in whom cerebrovascular disease, dementia, and metabolic disorders contribute to a higher incidence.3 Epilepsy accounts for significant morbidity, reduced quality of life, and increased mortality, particularly from sudden unexpected death in epilepsy (SUDEP), status epilepticus, and comorbid medical conditions.4
Overview of the ILAE Classification System
The ILAE classification system, which was updated in 2017 and again in 2025, organizes seizures by locus of onset in the brain, awareness during the event, and motor involvement, enabling clinicians to align observed behaviors with underlying pathophysiology (Table 1).5–9 The 2025 revision retains the four classes but removes onset from their names, replaces awareness with consciousness (defined by both awareness and responsiveness), replaces the motor and nonmotor distinction with observable and nonobservable manifestations, and consolidates 63 seizure types into 21.9 Seizures are classified into four main classes: focal, generalized, unknown (whether focal or generalized), and unclassified.
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