Epilepsy is a group of neurological disorders characterized by a tendency for recurrent, unprovoked seizures. A seizure is a sudden burst of abnormal electrical activity in the brain that can cause a variety of symptoms, ranging from brief lapses of awareness or muscle jerks to prolonged convulsions. These episodes can result in physical injuries, either directly, such as broken bones, or through causing accidents. The diagnosis of epilepsy typically requires at least two unprovoked seizures occurring more than 24 hours apart. In some cases, it may be diagnosed after a single unprovoked seizure if clinical evidence suggests a high risk of recurrence. Isolated seizures that occur without recurrence risk or are provoked by identifiable causes are not considered indicative of epilepsy.
The underlying cause is often unknown, but epilepsy can result from brain injury, stroke, infections, tumors, genetic conditions, developmental abnormalities, trauma, drowning, or an unidentified medical condition. In most cases, no structural or toxicological cause of death is found at autopsy. SUDEP can occur with or without evidence of a preceding seizure, and is often unwitnessed, especially during sleep.
Epilepsy that occurs as a result of other issues may be preventable. Diagnosis involves ruling out other conditions that can resemble seizures, and may include neuroimaging, blood tests, and electroencephalography (EEG).
Most cases of epilepsy, approximately 69%, can be effectively controlled with anti-seizure medications, and inexpensive treatment options are widely available. For those whose seizures do not respond to drugs, other approaches, such as surgery, neurostimulation or dietary changes, may be considered. Not all cases of epilepsy are lifelong, and many people improve to the point that treatment is no longer needed.
, approximately 50 million people worldwide have epilepsy, with nearly 80% of cases occurring in low- and middle-income countries. The burden of epilepsy in low-income countries is more than twice that in high-income countries, likely due to higher exposure to risk factors such as perinatal injury, infections, and traumatic brain injury, combined with limited access to healthcare. In 2021, epilepsy was responsible for an estimated 140,000 deaths, an increase from 125,000 in 1990.
Epilepsy is more common in both children and older adults. About 5–10% of people will have an unprovoked seizure by the age of 80. The chance of experiencing a second seizure within two years after the first is around 40%.
People with epilepsy may be treated differently in various areas of the world and experience varying degrees of social stigma due to the alarming nature of their symptoms. In many countries, people with epilepsy face driving restrictions and must be seizure-free for a set period before regaining eligibility to drive. The word epilepsy is from Ancient Greek , 'to seize, possess, or afflict'.
Signs and symptoms
Epilepsy is characterized by a long-term tendency to experience recurrent, unprovoked seizures. They may vary widely in their presentation depending on the affected brain regions, age of onset, and type of epilepsy.
Seizures
According to the 2025 classification by the International League Against Epilepsy (ILAE), seizures are grouped into four main classes: focal, generalized, unknown (whether focal or generalized), and unclassified.
Focal seizures Focal seizures originate in one area of the brain and may involve localized or distributed networks. For a given seizure type, the site of onset tends to be consistent across episodes. Once initiated, the seizure may remain localized or spread to adjacent areas, and in some cases, may propagate to the opposite hemisphere (contralateral spread).
They are further classified based on the state of consciousness during the episode:
Focal preserved consciousness seizure: the person remains aware and responsive. Focal impaired consciousness seizure: awareness and/or responsiveness are affected.
Experiences known as auras often precede focal seizures. The seizures can include sensory (visual, hearing, or smell), psychic, autonomic, and motor phenomena depending on which part of the brain is involved. Muscle jerks may start in a specific muscle group and spread to surrounding muscle groups, a pattern known as a Jacksonian march. Automatisms, or non-consciously generated activities, may occur; these may be simple repetitive movements like smacking the lips or more complex activities such as attempts to pick up something. Some focal seizures can evolve into focal-to-bilateral tonic-clonic seizures, where abnormal brain activity spreads to both hemispheres.
Generalized seizures Generalized seizures originate at a specific point within, and quickly spread across both hemispheres through interconnected brain networks. Although the spread is rapid, the onset may appear asymmetric in some cases. These seizures typically impair consciousness from the outset and can take several forms, including:
Generalized tonic–clonic seizures, often with an initial tonic phase followed by clonic jerking; Absence seizures, which may present with eye blinking or automatisms; Other generalized seizures, a category that includes tonic, clonic, myoclonic, atonic seizures and epileptic spasms.
Tonic–clonic seizures are among the most recognizable seizure types, typically involving sudden loss of consciousness, stiffening (tonic phase), and rhythmic jerking (clonic phase) of the limbs. This form of seizure (whether focal to bilateral, generalized, or of unknown onset) is associated with the highest risk of injury, medical complications, and sudden unexpected death in epilepsy (SUDEP).
Myoclonic seizures involve sudden, brief muscle jerks, which may affect specific muscle groups or the whole body. They can cause falls and injury. Absence seizures are characterized by brief lapses in awareness, sometimes accompanied by subtle movements such as blinking or slight head turning. The person typically recovers immediately afterward without confusion. Atonic seizures involve a sudden loss of muscle tone, often resulting in falls.
Triggers and reflex seizures Certain external or internal factors may increase the likelihood of a seizure in individuals with epilepsy. Common triggers include sleep deprivation, stress, fever, illness, menstruation, alcohol, and certain medications. These do not cause seizures by themselves, but lower the threshold in people who are already susceptible.
A small subset of individuals have reflex epilepsy, in which seizures are reliably provoked by specific stimuli. These reflex seizures account for about 6% of epilepsy cases. Common triggers include flashing lights (photosensitive epilepsy), sudden sounds, or specific cognitive tasks such as reading or performing calculations. In some epilepsy syndromes, seizures occur more frequently during sleep or upon awakening.
Seizure clusters Seizure clusters are multiple seizures occurring over a short period of time, with incomplete recovery between events. They are distinct from status epilepticus, though the two may overlap. Definitions vary across studies, but seizure clusters are typically described as two or more seizures within 24 hours or a noticeable increase in seizure frequency over a person's usual baseline. Estimates of their prevalence range widely (from 5% to 50% of people with epilepsy) largely due to differing definitions and populations studied. Seizure clusters are more common in individuals with drug-resistant epilepsy, high baseline seizure frequency, or certain epilepsy syndromes. They are associated with increased emergency care utilization, worse quality of life, impaired psychosocial functioning, and possibly elevated risk of mortality.
Postictal state After the active portion of a seizure (the ictal state) there is typically a period of recovery during which there is confusion, referred to as the postictal state, before a normal level of consciousness returns, lasting minutes to days. This period is marked by confusion, headache, fatigue, or speech and motor disturbances. Some may experience Todd's paralysis, a transient focal weakness. Postictal psychosis occurs in approximately 2% of individuals with epilepsy, particularly after clusters of generalized tonic–clonic seizures. in
Psychosocial Epilepsy can have substantial effects on psychological and social well-being. People with the condition may experience social isolation, stigma, or functional disability, which can contribute to lower educational attainment and reduced employment opportunities. These challenges often extend to family members, who may also encounter stigma and increased caregiving burden.
Several psychiatric and neurodevelopmental disorders are more common in individuals with epilepsy. These include depression, anxiety, obsessive–compulsive disorder (OCD), and migraine. Attention deficit hyperactivity disorder (ADHD) is particularly prevalent among children with epilepsy, occurring three to five times more often than in the general population. ADHD and epilepsy together can markedly affect behavior, learning, and social development. Epilepsy is also more common in children with autism spectrum disorder.
Approximately, one-in-three people with epilepsy have a lifetime history of a psychiatric disorder. This association is thought to reflect a combination of shared neurobiological mechanisms and the psychosocial impact of living with a chronic neurological condition. Some research also suggests that psychiatric conditions such as depression may precede the onset of epilepsy in certain individuals, particularly those with focal epilepsy. The nature of this association remains under investigation and may involve shared pathways, diagnostic overlap, or other confounding factors.According to Director of the Epilepsy and Clinical Neurophysiology Division and William G. Lennox Chair in the Department of Neurology at Boston Children's Hospital Phillip L. Pearl's research in epilepsy, particularly within inherited metabolic epilepsies such as succinic semialdehyde dehydrogenase deficiency (SSADHD), has emphasized the disorder as a systems-level neurophysiological condition rather than a purely seizure-centric entity.
Comorbid depression and anxiety are associated with poorer quality of life, increased healthcare utilization, reduced treatment response (including to surgery), and higher mortality. Some studies suggest that these psychiatric conditions may influence quality of life more than seizure type or frequency. Despite their clinical importance, depression and anxiety often go underdiagnosed and undertreated in people with epilepsy.
Causes
Epilepsy can result from a wide range of genetic and acquired factors, and in many cases, both play a role. Acquired causes include serious traumatic brain injury, stroke, brain tumors, and central nervous system infections. Despite advances in diagnostic tools, no clear cause is identified in approximately 50% of cases. The distribution of causes often varies with age. Epilepsies associated with genetic, congenital, or developmental conditions are more common in children, while epilepsy related to stroke or tumors is more frequently seen in older adults.
Seizures may also occur as a direct response to acute health conditions such as stroke, head trauma, metabolic disturbances, or toxic exposures. These are known as acute symptomatic seizures and are distinct from epilepsy, which involves a recurrent tendency to have unprovoked seizures over time.
The International League Against Epilepsy (ILAE) classifies the causes of epilepsy into six broad categories: structural, genetic, infectious, metabolic, immune, and unknown. These categories are not mutually exclusive, and more than one may apply in an individual case.
Structural