What is the most common cause of seizures?

Most Common Causes of Seizures

The most common causes of seizures include structural brain lesions (tumors, infection, infarction, traumatic brain injury, vascular malformations, developmental abnormalities), metabolic disturbances, and genetic factors. 1

Epidemiology and Classification

Seizures are extremely common, affecting approximately 10% of the population at some point in their lifetime 2. Active epilepsy (defined as doctor-diagnosed epilepsy requiring medication or having had seizures in the past year) affects about 1.2% of the US population, corresponding to approximately 3.4 million people 1.

Seizures are classified into three main categories:

• Focal onset: Arising within networks of a single cerebral hemisphere
• Generalized onset: Rapidly affecting both hemispheres
• Unknown onset: When the origin cannot be determined 1

Primary Causes of Seizures

Provoked (Acute Symptomatic) Seizures

These occur at the time of or within 7 days of an acute neurologic, systemic, metabolic, or toxic insult 1:

• Electrolyte abnormalities (especially hyponatremia)
• Drug or alcohol withdrawal
• Toxic ingestions
• Acute infections (encephalitis, meningitis)
• CNS mass lesions
• Traumatic brain injury

Unprovoked Seizures

These occur without acute precipitating factors and include:

• Remote symptomatic seizures (resulting from a CNS or systemic insult that occurred more than 7 days in the past)
• Idiopathic/genetic seizures
• Epilepsy (recurrent unprovoked seizures) 1

Age-Specific Causes

Neonates (0-29 days)

• Hypoxic-ischemic injury: By far the most common cause in neonates 1
• Other causes include:
  • Intracranial hemorrhage
  • Metabolic disturbances
  • Infections
  • Congenital malformations
  • Genetic disorders

Children and Adults

• Structural brain abnormalities
• Genetic factors
• Metabolic disorders
• Infections
• Trauma
• Vascular malformations 1

Diagnostic Approach

Neuroimaging

• CT Head: Rapid assessment for structural pathology such as hemorrhage, stroke, tumors, hydrocephalus in emergency situations 1
• MRI Brain: More sensitive for detecting lesions, especially in orbitofrontal and medial temporal regions, and small cortical lesions 1

Laboratory Testing

Key tests to identify metabolic causes:

• Electrolytes (sodium, calcium, magnesium)
• Glucose
• Renal and liver function tests
• Toxicology screen when indicated

Genetic Testing

Consider when clinical presentation suggests genetic epilepsy syndromes:

• Chromosomal microarray (CMA)
• Specific gene sequencing based on clinical presentation 3

Treatment Considerations

• Provoked seizures: Treatment focuses on correcting the underlying cause; antiepileptic drugs are generally not indicated long-term 4
• Unprovoked seizures: May require antiepileptic drugs, especially in patients at high risk for recurrence 2
• Status epilepticus: Requires immediate intervention with benzodiazepines followed by additional agents if seizures persist 1

Important Clinical Pearls

1. In patients with new-onset seizures, always search for a reversible cause before diagnosing epilepsy
2. Approximately 50% of epilepsy cases have no identifiable cause 5
3. About 35% of patients have refractory seizures that do not respond to medication 5
4. Non-convulsive status epilepticus should be considered in any patient with unexplained confusion or altered mental status 4
5. Most patients with provoked seizures do not develop epilepsy and do not require long-term anticonvulsant therapy 4

Remember that prompt identification and treatment of the underlying cause is crucial for preventing morbidity and mortality in patients presenting with seizures.