Definition and epidemiology
A seizure is a paroxysmal, time-limited event caused by abnormal, hypersynchronous electrical discharges of cortical neurons. It is distinct from epilepsy, which is a chronic disease defined by a predisposition to recurrent unprovoked seizures.
- Lifetime risk of experiencing at least one seizure is approximately 8-10%.
- Epilepsy prevalence is approximately 0.5-1% of the general population worldwide.
- Incidence is bimodal, highest in early childhood and again after age 60-65.
- Febrile seizures affect roughly 2-5% of children between 6 months and 5 years.
- Neonatal seizures (coded P90) are the most common neurologic emergency in the newborn period and often reflect hypoxic-ischemic encephalopathy or metabolic derangement rather than epilepsy.
- A single seizure is not epilepsy; epilepsy needs recurrence or high recurrence risk per ILAE criteria.
- Todd paralysis is transient postictal focal weakness, not a new stroke.
- Hypoglycemia and electrolyte abnormalities must be excluded first in any new seizure.
- Absence seizures have abrupt onset/offset with no postictal confusion, unlike complex partial seizures.
- Valproate is avoided in women of childbearing age due to teratogenicity; prefer lamotrigine or levetiracetam.
- Febrile seizures are common and usually benign, especially if simple (brief, generalized, no recurrence in 24h).
- Status epilepticus is defined by seizure activity lasting 5 minutes or more, or recurrent seizures without recovery.
- Mesial temporal sclerosis is a classic MRI finding in drug-resistant temporal lobe epilepsy.
Etiology and risk factors
Causes vary strongly by age group.
Provoked (acute symptomatic) causes
- Metabolic: hypoglycemia, hyponatremia, hypocalcemia, uremia, hepatic encephalopathy
- Toxic: alcohol withdrawal, cocaine, sympathomimetics, drug overdose
- Infectious: meningitis, encephalitis, febrile illness in children
- Structural/acute: stroke, traumatic brain injury, subarachnoid hemorrhage
- Eclampsia in pregnancy
Unprovoked (epilepsy-associated) causes
- Genetic/idiopathic generalized epilepsies (childhood and adolescent onset)
- Structural lesions: mesial temporal sclerosis, cortical dysplasia, tumor, old stroke scar, prior traumatic injury
- Neurodegenerative disease in the elderly
- Neonatal: hypoxic-ischemic encephalopathy, intracranial hemorrhage, inborn errors of metabolism, infection
Risk factors
- Family history of epilepsy
- Prior febrile seizures (especially complex ones)
- Head trauma, CNS infection, perinatal injury
- Developmental delay or structural brain abnormality
Pathophysiology
Seizures result from an imbalance between excitatory and inhibitory neurotransmission. Excessive excitation (glutamate-mediated) or insufficient inhibition (GABA-mediated) allows a group of neurons to fire synchronously and recruit adjacent cortex.
- Focal seizures arise from a localized cortical network (an epileptogenic focus) and may remain focal or spread to become bilateral.
- Generalized seizures involve bilateral cortical and subcortical networks from onset, often via thalamocortical circuits (classic in absence seizures).
- Ion channel dysfunction (sodium, calcium, chloride channelopathies) underlies many genetic epilepsies.
- Structural lesions create abnormal circuitry (e.g., mesial temporal sclerosis causes hyperexcitable hippocampal networks) that can act as a seizure focus.
- Status epilepticus develops when normal inhibitory mechanisms (GABA-A receptor internalization) fail, perpetuating continuous seizure activity and risking neuronal injury from excitotoxicity.
Clinical features
Presentation depends on seizure type and localization.
Focal seizures
- Aware (simple partial): preserved consciousness; motor, sensory, autonomic, or psychic symptoms (e.g., déjà vu, rising epigastric sensation)
- Impaired awareness (complex partial): automatisms (lip smacking, picking at clothes), staring, confusion
- May evolve to bilateral tonic-clonic (secondary generalization)
Generalized seizures
- Tonic-clonic: loss of consciousness, tonic stiffening then clonic jerking, tongue biting, incontinence, postictal confusion/lethargy
- Absence: brief (seconds) staring spells with abrupt onset/offset, no postictal confusion, common in children
- Myoclonic: brief shock-like jerks, often on awakening
- Atonic: sudden loss of muscle tone ("drop attacks")
Associated features
- Postictal state: confusion, fatigue, headache, sometimes transient focal weakness (Todd paralysis)
- Aura may precede focal-onset seizures
- Neonatal seizures: subtle findings such as eye deviation, lip smacking, cycling limb movements rather than classic tonic-clonic activity
Diagnosis
Diagnosis combines history, EEG, and neuroimaging; a single seizure is not sufficient to diagnose epilepsy unless recurrence risk is high.
- History: detailed eyewitness account of onset, duration, movements, tongue biting, incontinence, and postictal state is the most important diagnostic tool.
- EEG: supports diagnosis and classification; interictal epileptiform discharges increase diagnostic confidence but a normal EEG does not exclude epilepsy.
- MRI brain: preferred imaging to identify structural causes (mesial temporal sclerosis, tumor, cortical dysplasia, vascular malformation).
- Labs: glucose, electrolytes (sodium, calcium, magnesium), renal and liver function, toxicology screen, and in women of reproductive age, a pregnancy test.
- Lumbar puncture: if infection (meningitis/encephalitis) is suspected, after excluding mass effect.
- Neonates: additional metabolic workup (ammonia, lactate, inborn error of metabolism screening) given broader differential.
Diagnostic criteria for epilepsy (ILAE)
| Criterion | Description |
|---|---|
| Two unprovoked seizures | Occurring more than 24 hours apart |
| One unprovoked seizure | Plus a probability of further seizures similar to general recurrence risk (at least 60%) |
| Epilepsy syndrome diagnosis | Characteristic clinical and EEG features (e.g., childhood absence epilepsy) |
Differential diagnosis
- Syncope (vasovagal or cardiac): brief loss of consciousness, pallor, rapid recovery, may have brief myoclonic jerks (convulsive syncope)
- Psychogenic nonepileptic seizures (PNES): events without EEG correlate, often with closed eyes resisting opening, asynchronous thrashing
- Transient ischemic attack: focal deficit without positive motor/sensory phenomena, no postictal confusion
- Migraine with aura: slower progression of symptoms over minutes, often with headache
- Hypoglycemia: altered consciousness that resolves with glucose correction
- Sleep disorders: parasomnias, cataplexy, periodic limb movements
- Movement disorders: tics, paroxysmal dyskinesias
- Breath-holding spells in young children
Management
Management differs for an acute seizure/status epilepticus versus long-term epilepsy care.
Acute seizure and status epilepticus
- Ensure airway, oxygenation, and protect from injury; check glucose immediately.
- First-line: intravenous benzodiazepine (lorazepam or diazepam), or intramuscular/buccal/intranasal midazolam if no IV access.
- If seizure continues: second-line intravenous antiseizure drug such as fosphenytoin, valproate, or levetiracetam.
- Refractory status epilepticus: anesthetic infusion (propofol, midazolam infusion, or barbiturate) with ICU-level airway management and continuous EEG monitoring.
- Treat the underlying provoking cause (correct hypoglycemia/electrolytes, treat infection, manage withdrawal).
Long-term epilepsy management
- Antiseizure drug choice depends on seizure type: broad-spectrum agents (valproate, levetiracetam, lamotrigine) for generalized epilepsies; carbamazepine, lamotrigine, or levetiracetam commonly used for focal epilepsy.
- Valproate is generally avoided in women of childbearing potential due to teratogenicity; lamotrigine or levetiracetam are preferred alternatives.
- Monotherapy is preferred initially; combination therapy if seizures persist despite adequate first drug trial.
- Address modifiable triggers: sleep deprivation, alcohol, medication nonadherence, photic stimulation in photosensitive epilepsy.
- Surgical evaluation (resection, laser ablation, neurostimulation) for drug-resistant focal epilepsy, especially mesial temporal lobe epilepsy.
- Vagus nerve stimulation or responsive neurostimulation for selected drug-resistant cases not amenable to resection.
- Ketogenic diet is an option for certain drug-resistant pediatric epilepsies.
- Counsel on driving restrictions and safety precautions (water activities, heights) per local regulations; these vary by country and guideline body.
Complications and prognosis
- Status epilepticus carries significant morbidity and mortality if not treated promptly.
- Sudden unexpected death in epilepsy (SUDEP) is a rare but serious risk, more common in poorly controlled generalized tonic-clonic epilepsy.
- Injury risk: falls, aspiration, drowning, motor vehicle accidents during seizures.
- Psychosocial impact: depression, anxiety, stigma, and employment/driving limitations are common and should be screened for.
- Prognosis is favorable for many epilepsy syndromes: roughly 60-70% of patients achieve seizure freedom with appropriate antiseizure drug therapy.
- Febrile seizures in children generally carry an excellent prognosis with low risk of subsequent epilepsy, slightly higher with complex febrile seizures.
- Drug-resistant epilepsy (failure of two or more appropriately chosen antiseizure drugs) warrants referral to a comprehensive epilepsy center for further workup, including surgical candidacy.
VITAMIN CDE for seizure causes: Vascular, Infection, Trauma, Autoimmune/metabolic, Metabolic (glucose/electrolytes), Idiopathic/genetic, Neoplasm, Congenital, Drugs/toxins, Eclampsia.
Practice questions
1. A 22-year-old woman is brought to the emergency department by paramedics for jerking of all four limbs that has been continuous for the past 7 minutes. On arrival she remains actively convulsing with generalized tonic-clonic movements. Airway is maintained, oxygen is applied, and fingerstick glucose is normal. What is the most appropriate immediate next step?
2. A 6-year-old boy has recurrent brief episodes, several times daily, during which he stops talking and stares blankly for about 10 seconds, then immediately resumes his previous activity with no confusion. EEG shows generalized 3-Hz spike-and-wave discharges. Which seizure type best fits this presentation?
3. A 34-year-old woman with known epilepsy who is planning to conceive asks about adjusting her antiseizure medication. She currently takes valproate. Which change is most appropriate given her reproductive plans?
Frequently asked questions
What causes a seizure?
Seizures are caused by abnormal, excessive electrical discharges in the brain, triggered by metabolic disturbances (low glucose or sodium), infections, structural brain lesions, stroke, trauma, drug or alcohol withdrawal, or an underlying genetic epilepsy. In children, fever itself can provoke a febrile seizure. The specific cause often depends on the patient's age, since newborns, children, adults, and the elderly tend to have different predominant triggers.
What are the first symptoms of a seizure?
The first symptoms depend on seizure type but often include a brief aura (an unusual smell, rising stomach sensation, or déjà vu), sudden staring, unresponsiveness, or abnormal jerking movements. In generalized tonic-clonic seizures, sudden loss of consciousness and body stiffening typically come first, followed by rhythmic jerking. Afterward, confusion, fatigue, or headache (the postictal state) is common.
How is a seizure diagnosed?
Diagnosis relies mainly on a detailed description of the event from the patient or witnesses, supported by an EEG to detect abnormal brain electrical activity and an MRI to look for structural causes. Blood tests check for metabolic triggers like low glucose or sodium. A single event usually requires close follow-up rather than an immediate epilepsy diagnosis unless recurrence risk is high.
Is epilepsy curable?
Epilepsy is not always curable, but it is highly treatable; roughly 60-70% of people become seizure-free with the right antiseizure medication. Some epilepsy syndromes, especially certain childhood types, can be outgrown. For drug-resistant cases, surgery or neurostimulation can sometimes eliminate or greatly reduce seizures, though lifelong management is often still needed.
Seizure vs epilepsy — what is the difference?
A seizure is a single transient event of abnormal brain electrical activity, while epilepsy is a chronic disease defined by a tendency to have recurrent unprovoked seizures. One seizure caused by a clear trigger, like low blood sugar, does not mean someone has epilepsy. Epilepsy is diagnosed after two unprovoked seizures, or one seizure with a high likelihood of recurrence.
Key drugs
Related conditions and differentials
Sources and further reading
StatPearls (NCBI Bookshelf)MedlinePlusWHO ICD-10: P90
Educational content for medical students, prepared by the WhiteCoat Pro editorial team with AI assistance; every page is reviewed by a second AI model for factual errors. It is not medical advice and does not replace the product label, local guidelines or a clinician.