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Am Fam Physician. 2022;105(5):507-513

Patient information: See related handout on seizures in adults, written by the authors of this article.

This clinical content conforms to AAFP criteria for CME.

Author disclosure: No relevant financial relationships.

Seizures are transient signs and symptoms of abnormal, excessive, or synchronous neuronal activity in the brain. Up to 10% of adults have a seizure during their lifetime, with increasing incidence in people older than 55 years. One-third of people have a recurrent seizure within one year of an initial unprovoked seizure. Acute symptomatic (provoked) seizures recur less often, especially when provoking factors are addressed. After confirming a probable seizure, evaluation focuses on identifying provoking factors such as tumor, metabolic derangement, infectious disease, stroke, traumatic brain injury, medications, or substance misuse. Magnetic resonance imaging with an epilepsy protocol and electroencephalography should be performed as soon as practical. Lumbar puncture is useful if intracranial infection is suspected. Immediate initiation of anti-seizure medication reduces seizure recurrence by 35% within the first two years. Recurrence rates between three and five years are similar between patients who start anti-seizure medication immediately after the first seizure and those who do not. Restoration of driving privileges varies by state. After a seizure, safety concerns should be addressed, such as the need for a safety companion when bathing or swimming and the risks of ladders and other hazards.

The International League Against Epilepsy (ILAE) defines seizures as a transient occurrence of signs or symptoms due to abnormal, excessive, or synchronous neuronal activity in the brain.1 The ILAE categorizes seizures by the location of onset in the brain: focal, generalized, or unknown; they are subcategorized by the presence or absence of motor symptoms and loss of awareness.1

Clinical recommendationEvidence ratingComments
Evaluate patients for provoking factors after a first seizure. Provoking factors may be inflammatory, infectious, structural, toxic, or metabolic in nature and are found in 40% of first seizures.10 CExpert opinion based on epidemiologic studies
Use video-EEG monitoring during seizure-like activity to diagnose PNES, although up to 5% of patients diagnosed with PNES are eventually diagnosed with epilepsy.23,24 CExpert opinion and a single clinical study
Look for findings most predictive of a seizure, such as tongue biting, head turning or twisting, limb jerking, and urinary incontinence when evaluating a patient for possible seizures.16 BSingle study
Assess for history of medication or substance use that can provoke seizures through normal use, withdrawal, over-dose, drug-drug interaction, or impaired metabolism due to comorbidities.17,28,3033 CExpert opinion, case reports, and case series
Order an MRI with epilepsy-specific protocol and EEG as soon as possible after a first unprovoked seizure.9,18 CExpert opinion and guideline based on small to medium studies with inconsistent results
Recommend anti-seizure medications for patients with a high risk of seizure recurrence (e.g., patients with nighttime seizures, EEG abnormalities, history of brain insult, brain imaging abnormalities) after risks and benefits of treatment have been considered.21 CGuideline based on small clinical trials
Consider anti-seizure medications to reduce the risk of seizure recurrence by more than one-third at two years after a seizure. Recurrence rates are similar with or without medications after three years.21 CGuideline based on a systematic review of moderate-quality studies

In generalized onset seizures, abnormal electrical activity initiates throughout the brain. These types of seizures always include loss of awareness.1 Focal onset seizures begin in one area of the brain, although they may generalize to involve the entire brain and may or may not include loss of awareness.1 Motor symptoms can include the classic tonic-clonic movements as well as myoclonus or atonic seizures.1 Nonmotor symptoms of seizures may include emotional, sensory, and cognitive changes, or a lack of movement due to absence seizures.1

Most people with a first seizure do not have epilepsy. Epilepsy usually requires two unprovoked seizures occurring at least 24 hours apart, but the diagnosis can be made based on a single unprovoked seizure with at least a 60% risk of a second seizure in the next 10 years, or in the setting of an epilepsy syndrome.2 Determining the risk of a second seizure is an important part of the evaluation of the first seizure, although no formula exists to calculate risk and factors should be considered individually.

Epidemiology

The lifetime risk of having a seizure for an adult is up to 10%, although only 3% will be diagnosed with epilepsy.3 The incidence of a first seizure increases with age starting at approximately 55 years, with the highest risk in people older than 75 years.4

The rate of first seizures is higher in low-income countries than in the United States.5 Low- and middle-income countries account for approximately 80% of epilepsy worldwide. This may be because of higher rates of risk factors for epilepsy, such as congenital conditions, intracranial infections, and traumatic brain injury.5 In high-income countries, first seizures are more common in people affected by social and economic deprivation.6 Worldwide, seizures are increased where there is inadequate access to health care.7

Types of Seizures

ACUTE SYMPTOMATIC (PROVOKED) SEIZURES

Acute symptomatic seizures, also known as provoked or situation-related seizures, are manifestations of an acute insult to the central nervous system. Stroke and central nervous system infection are the most identified provoking factors.8 Other provoking factors include metabolic derangements, such as electrolyte abnormalities, or toxic effects of medications, alcohol, or drugs, including overdoses.9 Provoking factors may be infectious, inflammatory, metabolic, structural, or toxic in nature10 (Table 11115).

Infectious
Encephalitis
Meningitis
Neurocysticercosis
Prion disease
Toxoplasmosis
Tuberculosis
Inflammatory
Celiac disease
Hashimoto encephalitis
Other autoimmune conditions
Sarcoidosis
Systemic lupus erythematosus
Metabolic
Hepatic failure
Hypocalcemia (serum calcium < 8.5 mg per dL [2.13 mmol per L])
Hypoglycemia (blood glucose < 36 mg per dL [2 mmol per L]) or hyperglycemia (blood glucose > 450 mg per dL [24.98 mmol per L])
Hypomagnesemia (serum magnesium < 1.2 mg per dL [0.49 mmol per L])
Hyponatremia (serum sodium < 110 mEq per L [110 mmol per L])
Hypoxia
Porphyria
Renal failure
Structural
Arteriovenous malformations
Cerebrovascular accident
Intracranial lymphoma
Neurosurgery
Primary or secondary brain tumor
Traumatic brain injury
Toxic
Alcohol withdrawal
Prescribed medications (Table 2)
Substance misuse (e.g., cocaine, phencyclidine [PCP])
Other
Sleep deprivation

Approximately 40% of first seizures are associated with provoking factors. The evaluation after a first seizure should focus on identifying these factors10 (Figure 13,7,1620). This allows for the treatment of an underlying condition, or an assessment of an increased risk of seizure recurrence, to reduce the risk of subsequent seizures.7

UNPROVOKED SEIZURES

Unprovoked, or idiopathic, seizures do not have an acute cause identified on evaluation. Unprovoked seizures are most common in younger people.8 Unprovoked seizures are more likely to recur than those with a provoking cause found on evaluation.9

Unprovoked seizures are divided into two categories: those with no known etiology, and those related to progressive, preexisting, or remote central nervous system injury. Unprovoked seizures with known etiologies include prior traumatic brain injury, congenital cerebral palsy, and remote central nervous system infection.21 Unlike in acute symptomatic seizures, the central nervous system insult does not occur within the same time frame as the seizure. Recurrence is more common in unprovoked seizures with known etiologies.22

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