Causes of Seizures
Seizures are caused by a wide variety of conditions ranging from idiopathic cases to acute and chronic intracranial or systemic abnormalities, which require prompt identification and intervention to prevent morbidity and mortality. 1, 2
Classification of Seizures
- Seizures are classified into two main categories: provoked (acute symptomatic) and unprovoked seizures 1, 2
- Provoked seizures occur at the time of or within 7 days of an acute neurologic, systemic, metabolic, or toxic insult 1
- Unprovoked seizures 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) 1
- Epilepsy is defined as recurrent unprovoked seizures 1, 2
Structural/Neurological Causes
- Brain tumors (primary cerebral neoplasms and metastatic brain lesions) 1, 3
- Cerebrovascular disease including stroke and intracranial hemorrhage 1
- Traumatic brain injury 1
- Vascular malformations 1, 2
- Developmental abnormalities including malformations of cortical development 1, 2
- Hypoxic-ischemic injury (the most common cause of seizures in both term and preterm infants, accounting for 46-65% of neonatal seizures) 1
- Perinatal ischemic stroke (10-12% of neonatal seizures) 1
Metabolic and Systemic Causes
- Electrolyte abnormalities (particularly hyponatremia) 1, 4
- Hypoglycemia 2, 5
- Uremia and renal failure 4
- Hepatic failure 4
- Hypoxia 4
Toxic Causes
- Medication toxicity (including theophylline, isoniazid) 4
- Drug and alcohol withdrawal 1, 5
- Drug overdose 5
Infectious Causes
- Encephalitis 1, 5
- Meningitis 4
- Brain abscess 1
- Infections are more likely to cause seizures in neonates when occurring beyond the seventh day of life 1
Genetic Causes
- Genetic disorders (particularly in neonates with seizures occurring beyond the seventh day of life) 1
- Idiopathic epilepsy syndromes 6
Other Causes
- Febrile seizures (occur between 6 months and 5 years of age, associated with fever but without evidence of intracranial infection) 1
- Autoimmune disorders 7
Clinical Implications
- Approximately 10% of the population will have one or more seizures during their lifetime 6
- Epilepsy affects 1-3% of the population 6
- Mortality rates are 4-7 times higher in people with medically refractory seizures 8
- The incidence of acute symptomatic seizures is 29-39 per 100,000 per year, predominating in men, in the youngest age class, and in the elderly 7
- The incidence of single unprovoked seizures is 23-61 per 100,000 person-years 7
Diagnostic Approach
- Brain imaging (MRI or CT) is essential for identifying structural causes of seizures 1, 5
- MRI has greater sensitivity for detecting intracranial developmental abnormalities associated with seizures 1
- EEG helps identify the region of the brain where the seizure originated and guides initial diagnostic testing 6
- Laboratory tests to identify metabolic and toxic causes 4