What are the guidelines for classifying and managing seizures according to the International League Against Epilepsy (ILAE)?

ILAE Classification and Management of Seizures

The International League Against Epilepsy (ILAE) 2017 classification system is the current standard for classifying seizures, with the fundamental distinction being between focal, generalized, and unknown onset seizures, which guides appropriate treatment selection and prognostication. 1, 2, 3

Seizure Classification Framework

Level 1: Seizure Onset

• Focal onset: Seizures arising within networks limited to one hemisphere
• Generalized onset: Seizures engaging bilateral networks from onset
• Unknown onset: When onset is not clearly determined

Level 2: Awareness in Focal Seizures

• Focal aware seizures: Consciousness preserved throughout (formerly "simple partial")
• Focal impaired awareness seizures: Consciousness affected at any point (formerly "complex partial")

Level 3: Motor vs. Non-Motor Features

Focal Motor Seizures:

• Automatisms: Semi-purposeful, repetitive movements
• Atonic: Sudden loss of muscle tone
• Clonic: Rhythmic jerking
• Epileptic spasms: Brief contractions of trunk and limbs
• Hyperkinetic: Excessive, irregular movements
• Myoclonic: Brief, shock-like jerks
• Tonic: Sustained stiffening

Focal Non-Motor Seizures:

• Autonomic: Changes in autonomic function (heart rate, pupil size, etc.)
• Behavior arrest: Activity cessation
• Cognitive: Impaired language, thinking
• Emotional: Fear, anxiety, joy
• Sensory: Altered sensations

Generalized Motor Seizures:

• Tonic-clonic: Stiffening followed by rhythmic jerking
• Clonic: Rhythmic jerking
• Tonic: Stiffening
• Myoclonic: Brief muscle jerks
• Myoclonic-tonic-clonic: Myoclonic jerks followed by tonic-clonic activity
• Myoclonic-atonic: Jerks followed by loss of tone
• Atonic: Sudden loss of muscle tone
• Epileptic spasms: Brief contractions

Generalized Non-Motor Seizures (Absence):

• Typical absence: Brief staring spells with immediate recovery
• Atypical absence: Longer episodes with slower onset/offset
• Myoclonic absence: Absence with rhythmic myoclonic movements
• Eyelid myoclonia: Eyelid jerks with or without absence 2, 4, 3

Epilepsy Definition and Classification

Epilepsy is defined by ILAE as having:

1. At least two unprovoked seizures occurring >24 hours apart, OR
2. One unprovoked seizure with high recurrence risk (similar to after two unprovoked seizures) over 10 years, OR
3. Diagnosis of an epilepsy syndrome 1, 5

Epilepsies are classified as:

• Focal epilepsy
• Generalized epilepsy
• Combined generalized and focal epilepsy
• Unknown epilepsy

Etiologic Classification

The ILAE emphasizes identifying etiology, categorized as:

• Structural: Visible abnormality on imaging
• Genetic: Known or presumed genetic cause
• Infectious: Direct result of infection
• Metabolic: Metabolic disorder
• Immune: Immune-mediated
• Unknown: Cause not yet determined 5, 6

Diagnostic Approach

EEG Evaluation

• Essential for detecting epileptic activity
• Helps distinguish epileptic from non-epileptic events
• Continuous EEG monitoring valuable for status epilepticus 5

Neuroimaging

• MRI: Superior for identifying epileptogenic lesions, especially for focal seizures
• CT: Limited role in generalized seizures (only 6% positive findings), but useful in acute trauma settings for identifying hemorrhage or mass effect 5

Differentiating Seizures from Mimics

Seizures vs. Syncope

• Seizures: Typically last ~1 minute, may have synchronous movements
• Syncope: Movements last seconds, usually asynchronous, occur after loss of consciousness
• Tongue biting: In epilepsy, typically lateral; in syncope, typically at tip 1
• Recovery: Immediate clearheadedness in syncope; prolonged confusion in epilepsy 1

Seizures vs. Psychogenic Non-Epileptic Seizures (PNES)

• PNES: Often have pelvic thrusting, waxing/waning intensity, closed eyes during unconsciousness
• Epileptic seizures: More stereotyped, eyes typically open 1

Treatment Principles

Treatment selection depends primarily on seizure type:

• Focal seizures: Levetiracetam often first-line due to favorable side effect profile
• Generalized seizures: Valproate effective but has significant drug interactions; alternatives include lamotrigine and topiramate
• Status epilepticus: Benzodiazepines first-line, followed by sodium valproate, levetiracetam, phenytoin, propofol, or barbiturates 5

Common Pitfalls to Avoid

1. Failing to distinguish between epileptic and non-epileptic events
2. Missing non-convulsive status epilepticus in patients with altered mental status
3. Using anticonvulsants with significant drug interactions in patients on multiple medications
4. Not recognizing that new-onset or poorly controlled seizures may indicate underlying disease progression 5

Impact on Quality of Life

Seizure control significantly impacts quality of life for patients and caregivers. Treatment should always prioritize reduction in morbidity, mortality, and improvement in quality of life through appropriate classification, diagnosis, and management 5.