NeuroLogic: ILAE Classification
Choose the task below: classify an event, classify an established epilepsy, or look up a syndrome. For the board-level read of the 2022 framework, start in Board Review, section 6.1. For ICU EEG terms, use EEG Fundamentals.
Classify the event using the 2025 seizure classes, then describe what happened in sequence. This is Level 1 of the ILAE framework; Levels 2 and 3 are under Classify the epilepsy.
Describe observable and non-observable manifestations in chronological order. If consciousness cannot be determined, retain the parent class; do not guess. The 2017 awareness and motor/non-motor labels are historical terminology.
Read the ILAE 2025 seizure classification PDFEpileptic seizure
Then describe what happened, in order: observable signs (motor, automatisms, autonomic) and non-observable ones (sensory, cognitive, emotional).
Choose a class to read its definitions and subtypes.
Abbreviations follow ILAE 2025 Table 1. Neonatal seizures are classified in a separate ILAE position paper and are not included here.
Focal seizures originate in networks limited to one hemisphere of the brain, with onset consistent from one seizure to another (they may later spread, but initial onset is localized). In the updated classification, focal seizures are further classified by the patient's state of consciousness during the seizure – either preserved or impaired.
A focal seizure with preserved awareness and responsiveness. Ask about later recall and responses during the event, compared with the person's baseline. Consider aphasia, paresis, or isolated amnesia before interpreting a failed response or memory gap. The 2017 term was “focal aware seizure”; the older term “simple partial seizure” is no longer recommended.
A focal seizure with impaired awareness or impaired responsiveness at any point during the seizure, after considering alternative explanations such as aphasia or paresis. The 2017 term was “focal impaired-awareness seizure”; the older term “complex partial seizure” is no longer recommended.
A seizure that begins focally and then spreads to involve both hemispheres, resulting in a bilateral tonic-clonic seizure. Formerly called "secondary generalized tonic-clonic."
Generalized seizures originate at some point within, and rapidly engage, bilaterally distributed networks (the seizure activity is widely distributed across networks of the brain at start). Consciousness is typically impaired to some degree in generalized seizures, though for certain brief types awareness may be preserved.
Absence seizures are generalized seizures characterized by brief impairment of consciousness (usually a sudden behavioral arrest and vacant stare). Typically last 5-20 seconds with abrupt onset and offset. Motor features may be present in some absence types.
Convulsive seizures featuring a sequence of tonic contraction followed by clonic jerking of the limbs ("grand mal"), with loss of consciousness
This category is used when it is unknown whether a seizure is focal or generalized in onset. Typically, this occurs if a seizure was unwitnessed or lacks sufficient data (e.g. occurred during sleep or without EEG) to determine the initial onset.
A seizure of indeterminate onset during which consciousness was preserved (the person remained aware and responsive).
A seizure of indeterminate onset in which consciousness was impaired. Applies when someone has a loss of awareness during the event but there's no information on how the seizure began.
Unknown-onset bilateral tonic-clonic (BTC). A convulsive seizure featuring tonic then clonic phases was observed, but it is uncertain whether it began focally or was generalized from the start.
Use when an event is confidently epileptic but available information is insufficient to classify. This is an interim category that should be updated when more information becomes available.
Examples illustrating the practical application of the 2025 ILAE seizure classification. Abbreviations follow ILAE 2025 Table 1.
Examples adapted from the 2025 ILAE Classification of Epileptic Seizures. Terminology reviewed September 2026.
The ILAE framework is an order of questions, not a list: the seizure type, then the epilepsy type, then whether a syndrome fits. Each level answers something the one before it cannot. Etiology and comorbidities are considered at every level.
Read the ILAE 2017 epilepsy classificationThe framework starts with the event: focal, generalized, unknown, or unclassified. Seizure types now follow the 2025 classification, which replaced the 2017 seizure types this framework first used.
Classification can stop here when there is not enough information to go further, such as after a single seizure.
A different question from Level 1: this classifies the disease, not the event, and it assumes a diagnosis of epilepsy has already been made. Someone can have focal seizures and still not have focal epilepsy.
At Level 2, medication choice depends on seizure types as well as epilepsy type. Carbamazepine and oxcarbazepine can aggravate absence or myoclonic seizures; this is not a uniform effect of every medication with sodium-channel activity.
A syndrome is a recognizable cluster that travels together: seizure types, EEG and imaging features, an age-dependent pattern of onset and often of remission, plus triggers, diurnal variation, and characteristic comorbidities.
A syndrome diagnosis buys you things the first two levels cannot: expected course, specific drug choices and drugs to avoid, genetic counseling, and a prognosis to give the family. Not every epilepsy fits one, and saying so is better than forcing a label.
Etiology is not a fourth step. It runs alongside all three levels and is reconsidered as information arrives. More than one category can apply at once.
Comorbidities are considered at every level too — learning, developmental, psychiatric and behavioral. In several syndromes they, not the seizures, determine long-term outcome.
