Medical Terminologies Used for Seizures
The International League Against Epilepsy (ILAE) 2017 classification system organizes seizures into three primary onset categories: focal onset, generalized onset, and unknown onset, with specific subcategories based on motor/nonmotor features and level of awareness. 1
Core Terminology Framework
Primary Seizure Onset Classifications
The fundamental structure divides all seizures into:
- Focal onset seizures: Arise within networks of a single cerebral hemisphere 1
- Generalized onset seizures: Rapidly affect both hemispheres and both sides of the body from onset 1
- Unknown onset seizures: When the beginning of the seizure is unobserved or unclear 2
Focal Seizure Descriptors
Focal seizures are characterized along two key dimensions:
Level of Awareness:
- Aware: Patient maintains awareness/recall during the seizure 2
- Impaired awareness: Patient has altered consciousness or inability to recall events 2
Motor vs. Nonmotor Features:
- Motor onset: Includes automatisms, behavior arrest, hyperkinetic, atonic, clonic, epileptic spasms, myoclonic, and tonic seizures 2
- Nonmotor onset: Includes autonomic, cognitive, and emotional features 2
Focal to bilateral tonic-clonic: Replaces the outdated term "secondarily generalized seizure" 2
Generalized Seizure Types
Motor generalized seizures:
- Tonic-clonic
- Absence with eyelid myoclonia
- Myoclonic
- Myoclonic-atonic
- Myoclonic-tonic-clonic
- Atonic
- Clonic
- Tonic
- Epileptic spasms 2
Nonmotor generalized seizures:
- Primarily absence seizures 1
Epilepsy-Related Terminology
Epilepsy definition (ILAE): Requires one of three criteria:
- At least two unprovoked seizures occurring >24 hours apart
- One unprovoked seizure with probability of recurrence similar to general risk after two seizures (over next 10 years)
- Diagnosis of an epilepsy syndrome 1
Active epilepsy: History of doctor-diagnosed epilepsy/seizure disorder with current medication use OR one or more seizures in the past year 1
Status Epilepticus Terminology
Status epilepticus: Epileptic seizure sufficiently prolonged or repeated at brief intervals to produce an unvarying and enduring epileptic condition 3
- Traditional definition: ≥30 minutes of persistent seizures or recurrent seizures without complete return to consciousness between episodes 3
- Modern proposed threshold: 5 minutes (some authors advocate shortening from 30 minutes) 3
Subtypes:
- Convulsive status epilepticus (CSE): Generalized tonic-clonic status epilepticus 4
- Nonconvulsive status epilepticus (NCSE): Requires EEG for diagnosis 4
- Refractory status epilepticus (RSE): Failure to respond to first-line therapies 4
- Super-refractory status epilepticus (SRSE): Continues despite anesthetic treatment 4
Etiologic Classification Terms
Acute symptomatic seizure: Result of an acute process 3
Remote symptomatic seizure: Result from past intracranial insult (stroke, trauma, anoxia) 3
Provoked vs. unprovoked seizures: Critical distinction for epilepsy diagnosis 1
Immediate vs. late seizures (trauma-related): Immediate seizures from force of injury itself; late seizures occurring subsequently 1
Obsolete Terms to Avoid
The 2017 ILAE classification eliminated these outdated terms:
- "Partial" (replaced by "focal") 2
- "Simple partial" 2
- "Complex partial" 2
- "Dyscognitive" 2
- "Psychic" 2
- "Secondarily generalized" (replaced by "focal to bilateral tonic-clonic") 2
Clinical Application Notes
Critical pitfall: The classification is operational and practical, not based on fundamental mechanisms, as basic seizure mechanisms remain incompletely understood 1. This means classification relies on observable clinical features rather than underlying pathophysiology.
Semiology (symptoms and signs) forms the foundation for grouping seizures under these categories 5. The system allows classification even when onset is unobserved and includes previously unclassifiable seizure types 2.
The 2017 system emphasizes etiology identification at all classification stages, recognizing structural brain lesions (tumors, infection, infarction, traumatic brain injury, vascular malformations, developmental abnormalities) as important etiologic factors 1.