Seizure Etiologies and Classifications
Classification and Causes
- Seizures are fundamentally divided into provoked (acute symptomatic) and unprovoked categories, with provoked seizures occurring at the time of or within 7 days of an acute insult, while unprovoked seizures occur without acute precipitating factors, as stated by the American College of Emergency Physicians 1
- Hyperglycemia can precipitate seizures, particularly in diabetic emergencies, according to the American College of Emergency Physicians 1
- Hyponatremia and other electrolyte abnormalities are common precipitants of seizures, as noted by the American College of Emergency Physicians 1
- Hypocalcemia and hypomagnesemia, particularly in patients with renal failure or chronic alcoholism, can cause seizures, as reported by the American College of Emergency Physicians 1
- Uremia in renal failure patients is a known cause of seizures, as stated by the American College of Emergency Physicians 1
- Toxic ingestions, including cocaine, tricyclic antidepressants, antihistamines, and theophylline, can cause seizures, according to the American College of Emergency Physicians 1 and 2
- Encephalitis is a critical infectious etiology requiring urgent intervention, as noted by the American College of Emergency Physicians 1
- CNS infections, including meningitis, can cause seizures, particularly in immunocompromised patients, as reported by the American College of Emergency Physicians 2 and 3
- CNS mass lesions, including tumors and brain masses, can cause seizures, as stated by the American College of Emergency Physicians 1 and the American College of Radiology 4
- Stroke and cerebral infarction are common causes of seizures, with incidence increasing with age, according to the American College of Emergency Physicians 3 and the American College of Radiology 4
- Traumatic brain injury can cause both immediate and late seizures, as reported by the American College of Radiology 4
- Intracranial hemorrhage, including subdural hematomas, can cause seizures, as noted by the American College of Emergency Physicians 3
- Vascular malformations can cause seizures, as stated by the American College of Emergency Physicians 3
- Idiopathic epilepsy represents seizures without identifiable structural or metabolic cause, as reported by the American College of Emergency Physicians 1 and 3
- Genetic epilepsy syndromes, particularly in pediatric populations, can cause seizures, as noted by the American College of Radiology 5
- Prior stroke occurring more than 7 days before seizure onset can cause unprovoked seizures, as stated by the American College of Emergency Physicians 1
- Remote traumatic brain injury can cause unprovoked seizures, as reported by the American College of Emergency Physicians 1
- Malformations of cortical development can cause unprovoked seizures, as noted by the American College of Radiology 5
- HIV patients with new-onset seizures require consideration of CNS toxoplasmosis, lymphoma, cryptococcal meningitis, and HIV encephalopathy, as reported by the American College of Emergency Physicians 2
- Immunocompromised patients have higher rates of infectious etiologies, as stated by the American College of Emergency Physicians 3
- Hypoxic ischemic injury is the most common cause of neonatal seizures, as noted by the American College of Radiology 5
- Intracranial hemorrhage and perinatal ischemic stroke are common causes of neonatal seizures, as reported by the American College of Radiology 5
- Approximately 90% of hypoxic ischemic encephalopathy seizures occur within 2 days of birth, as stated by the American College of Radiology 5
- An underlying cause can be identified in approximately 95% of neonatal seizures, as noted by the American College of Radiology 5
- History and physical examination predict most metabolic abnormalities except occasional cases of hypoglycemia and subdural hematomas, as reported by the American College of Emergency Physicians 3
- Fever in seizure patients warrants strong consideration of CNS infection, as stated by the American College of Emergency Physicians 3
- Focal neurologic examination findings have 97% correlation with symptomatic seizures, as noted by the American College of Emergency Physicians 3
Seizure Etiology and Classification
Introduction to Seizure Causes
- 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, as noted by the American College of Radiology 6, 7
Classification of Seizures
- Seizures are classified as provoked (acute symptomatic) or unprovoked, with epilepsy defined as recurrent unprovoked seizures, according to Praxis Medical Insights 7
- Seizures represent an extremely heterogeneous group of medical conditions ranging from benign cases to life-threatening situations such as status epilepticus, as reported by the American College of Radiology 6, 8
Structural/Neurological Causes
- Intracranial hemorrhage and perinatal ischemic stroke (10-12%) are common causes of neonatal seizures, as identified by the American College of Radiology 6, 8
- Hypoxic ischemic injury is the most common cause of seizures in both term and preterm infants (46-65%), according to the American College of Radiology 6, 8
- Malformations of cortical development and other structural brain anomalies can cause seizures, as noted by the American College of Radiology and Praxis Medical Insights 6, 7, 8
Metabolic and Systemic Causes
- Hypoglucemia is a significant metabolic cause of seizures, as reported by Praxis Medical Insights 7
Infectious Causes
- Infections such as encephalitis can cause seizures, according to Praxis Medical Insights 7
- Seizures occurring beyond the seventh day of life in neonates are more likely related to infections, as identified by the American College of Radiology 6, 8
Causes of First Seizure in Adults
Diagnostic Approach
- The American College of Emergency Physicians recommends that all patients with first seizures undergo laboratory evaluation, including complete blood count, comprehensive metabolic panel, and toxicology screen when appropriate, as approximately 8% of seizure patients have correctable metabolic abnormalities 9, 10
- The American College of Emergency Physicians suggests that emergent neuroimaging is required for patients with persistent focal deficits or failure to return to baseline within several hours, with CT scan being essential in evaluation of all adults with first seizure to identify structural lesions 9
Provoked Seizures
- Cocaine use can cause seizures in approximately 10% of cocaine-related medical admissions, with 70% being single, generalized seizures 9
- Alcohol withdrawal is a common cause of seizures, though clinicians must eliminate other symptomatic causes before labeling seizures as withdrawal-related 9
Incidence and Characteristics of Post‑Stroke Seizures
Timing of Seizures
- Early (acute symptomatic) seizures occur within the first 7 days after a cerebrovascular accident, most frequently within the initial 24 hours. 11, 12
Incidence in the Acute Phase
- Between 4 % and 10 % of patients experience seizures during the acute period after stroke; the actual risk is thought to be nearer the lower end of this range. 11, 12, 13
Typical Seizure Phenotype
- Early seizures are more common than late (unprovoked) seizures and usually present as focal motor seizures, which may or may not evolve into secondary generalization. 11, 12, 13