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ILAE Classification of Epilepsy - update


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Title: ILAE Classification of Epilepsy - update

ILAE Classification of Epilepsy - update
  • Chris Rittey
  • Sheffield

ILAE classification schemes
  • 1960 first suggested ILAE classification
  • 1981 seizure classification published
  • 1989 syndrome classification published
  • 2001, 2006 attempts at update

  • Revised terminology and concepts for organization
    of the epilepsies Report of the Commission on
    Classification and Terminology
  • Developed as a methodologically and conceptually
    sound and meaningful revision to the
    classifications of 1981 and 1989
  • Based on input from genetics, neuroimaging,
    therapeutics, paediatric and adult epileptology,
    statistics, research design

What is a classification of epilepsy?
  • A list of entities which are recognised to be
    distinct forms of epilepsy
  • No new entities added since 2006 report
  • The concepts and structure underpinning that list
  • 1989 classification recognised as an organisation
    built on concepts rather than true classification
  • Accordingly the current organisation is being
  • Mechanism and process to determine which entities
    are included on that list and the features which
    characterise them this needs to be agreed under
    new system


Seizure classification generalised seizures
  • Considered to originate at some point within, and
    rapidly engage, bilaterally distributed networks
  • Networks can include cortical and sub-cortical
    structures but do not necessarily include the
    entire cortex
  • Individual seizures may have an apparently
    localised onset but location and lateralisation
    are not consistent from one seizure to another
  • Generalised seizures can be asymmetrical

Seizure classification - focal seizures
  • Considered to originate within networks limited
    to one hemisphere
  • May be discretely localised or more widely
  • May arise in sub-cortical structures
  • Ictal onset is consistent from one seizure to
    another for each seizure type
  • Preferential propagation patterns occur may
    involve the contralateral hemisphere
  • There may be more than one epileptogenic network
    and more than one seizure type in an individual
    but each has a consistent site of onset

Specific changes to 1981 schema
  • Neonatal seizures no longer regarded as a
    separate entity
  • Sub-classification of absences has been
  • Myoclonic absence and absence with eyelid
    myoclonia now recognised
  • Epileptic spasms included in their own category
  • Generalised, focal, or of unclear onset

Specific changes to 1981 schema
  • Distinction between different types (e.g. simple
    and complex partial) is eliminated however
    importance of impairment of consciousness,
    localisation, ictal progression recognised as
    potentially important for individual patients
  • Focal seizures can be described using these
  • Myoclonic atonic (myoclonic astatic) seizures now
  • Category of unclassified epileptic seizures no
    longer accepted

Classification strata
  • Classification of seizures
  • Syndromes and epilepsies
  • Aetiological designation
  • Other dimensions
  • IV-A. Age at onset
  • IV-B. Natural evolution
  • IV-C. Other features

I. Classification of seizures
  • Tonic clonic (in any combination)
  • Absence - typical
  • - atypical
  • - absence with special
  • - myoclonic absence
  • - eyelid myoclonia
  • Myoclonic - myoclonic
  • - myoclonic atonic
  • - myoclonic tonic
  • Clonic
  • Tonic
  • Atonic
  • Epileptic spasms

Descriptors of focal seizures
  • Without impairment of consciousness/responsiveness
  • With observable motor or autonomic components
    (corresponds to simple partial seizure)
  • Involving subjective sensory or psychic phenomena
    only (corresponds to aura)
  • With impairment of consciousness/responsiveness
    (corresponds to complex partial seizure)
  • Evolving to a bilateral convulsive seizure
    (involving tonic, clonic or tonic and clonic
    components) replaces secondary generalised

II. Syndromes and epilepsies
  • Need to recognise the different levels of
    specificity between syndromes
  • In previous classification
  • Some syndromes very specific and well
    differentiated e.g. CAE
  • Other syndromes very poorly differentiated e.g.
    cryptogenic parietal lobe epilepsy
  • New system attempts to explicitly acknowledge
    these differences

  • Syndromes will no longer be characterised as
    being focal or generalised

Classification groups
  • Electroclinical syndromes
  • Epilepsy constellations
  • Epilepsies secondary to specific structural or
    metabolic lesions or conditions
  • Epilepsies of unknown cause

Electro-clinical syndromes I
  • Complex of clinical features, signs and symptoms
    that define a distinctive, recognisable clinical
  • Use of term syndrome will be restricted to a
    group of clinical entities that are reliably
    identified by a cluster of electroclinical and
    developmental relationships
  • Largely (not exclusively) genetic
  • Tend to have strong relationship to developmental
    aspects of the brain

Electro-clinical syndromes II
  • Identifiable on the basis of
  • Typical age of onset
  • Specific EEG characteristics
  • Specific seizure types and other clinical
  • Diagnosis has implications for treatment,
    management and prognosis

Epilepsy constellations
  • Epilepsy entities which are not syndromes per se
    but represent clinically distinctive collections
    of features
  • Often have implications for treatment, esp.
  • Include
  • Temporal lobe epilepsy (with hippocampal
  • Gelastic seizures with hypothalamic hamartoma
  • Rasmussen syndrome
  • Age at presentation is not a defining feature

Epilepsies secondary to specific lesions or
  • Lower level of specificity than previous groups
  • Previously defined on basis of localisation e.g.
    symptomatic temporal lobe epilepsy
  • Now recommended that emphasis is placed on the
    aetiology e.g. epilepsy with focal features
    secondary to focal cortical dysplasia in the
    temporal lobe
  • Now included in the classification within the
    group Structural/metabolic epilepsies

Epilepsies of unknown cause
  • Includes all epilepsies previously known as
  • Account for 1/3 or more of all people with
  • Probably need to move away from attempting to
    classify by interictal spike focus replace with
    detailed description of relevant features
  • Age at onset
  • EEG features
  • Cognitive/developmental assessment
  • Diurnal patterns of seizure occurrence
  • Will allow improved classification with time

Electro-clinical syndromes and other epilepsies
  • Electro-clinical syndromes arranged by age at
  • Neonatal period         Benign familial neonatal
    seizures (BFNS)         Early myoclonic
    encephalopathy (EME)         Ohtahara syndrome
  • Infancy         Migrating partial seizures of
    infancy         West syndrome         Myoclonic
    epilepsy in infancy (MEI)         Benign
    infantile seizures         Benign familial
    infantile seizures         Dravet
    syndrome         Myoclonic encephalopathy in
    nonprogressive disorders

Electro-clinical syndromes and other epilepsies
  • Childhood         Febrile seizures plus (FS)
    (can start in infancy)         Early onset benign
    childhood occipital epilepsy (Panayiotopoulos
    type)         Epilepsy with myoclonic atonic
    (previously astatic) seizures         Benign
    epilepsy with centrotemporal spikes
    (BECTS)         Autosomal-dominant nocturnal
    frontal lobe epilepsy (ADNFLE)         Late onset
    childhood occipital epilepsy (Gastaut
    type)         Epilepsy with myoclonic
    absences         Lennox-Gastaut syndrome        
    Epileptic encephalopathy with continuous
    spike-and-wave during sleep (CSWS)        
                  including Landau-Kleffner syndrome
    (LKS)         Childhood absence epilepsy (CAE)

Electro-clinical syndromes and other epilepsies
  • Adolescence - Adult         Juvenile absence
    epilepsy (JAE)         Juvenile myoclonic
    epilepsy (JME)         Epilepsy with generalized
    tonic-clonic seizures alone         Progressive
    myoclonus epilepsies (PME)         Autosomal
    dominant partial epilepsy with auditory
    features (ADPEAF)         Other familial temporal
    lobe epilepsies

Electro-clinical syndromes and other epilepsies
  • Less Specific Age Relationship         Familial
    focal epilepsy with variable foci (childhood to
    adult)         Reflex epilepsies   
  • Distinctive Constellations         Mesial
    temporal lobe epilepsy with hippocampal
    sclerosis (MTLE with HS)         Rasmussen
    syndrome         Gelastic seizures with
    hypothalamic hamartoma
  • Epilepsies that do not fit into any of these
    diagnostic categories can be distinguished first
    on the basis of the presence or absence of a
    known structural or metabolic condition (presumed
    cause) and then on the basis of the primary mode
    of seizure onset (generalized versus focal).

Electro-clinical syndromes and other epilepsies
  • Epilepsies attributed to and organized by
    structural-metabolic causes
  • Malformations of Cortical development
    (hemimeganencephaly, hetertopias
    etc) Neurocutaneous syndromes (Tuberous sclerosis
    complex, Sturge-Weber, etc) Tumor Infection Trauma
    Angioma Peri-natal insults Stroke Etc.

Electro-clinical syndromes and other epilepsies
  • Epilepsies of unknown cause
  • Conditions with epileptic seizures that are
    traditionally not diagnosed as a form of epilepsy
    per se.         Benign neonatal seizures
    (BNS)         Febrile seizures (FS)

III. Aetiological designation
  • Withdrawal of concepts of idiopathic, cryptogenic
    and symptomatic
  • Three main aetiological groups
  • Genetic - the epilepsy is the direct result of a
    known or presumed genetic defect in which
    seizures are the core symptom
  • Structural/metabolic the epilepsy results from
    the structural or metabolic condition, not simply
    as a result of the genetic cause of the condition
  • Unknown cause

IV. Other dimensions
  • IV-A. Age at onset
  • Neonatal (lt 44 weeks gestational age)
  • Infant (lt 2 years)
  • Child (2-12 years)
  • Adolescent (12-18 years)
  • Adult (gt 18 years)

IV. Other dimensions
  • IV-B. Natural evolution
  • Epileptic encephalopathy can be used to
    characterise syndromes as well as individuals.
    Need to recognise that source of encephalopathy
    is usually unknown.
  • Benign key features
  • Seizures are self-limited i.e. spontaneous
    remission, regardless of treatment, occurs at an
    expected age and is the anticipated outcome
  • Seizures themselves are not disabling over the
    course of the active epilepsy does not preclude
    subtle/moderate cognitive and behavioural
  • Pharmaco-responsive

IV. Other dimensions
  • IV-C. Other features
  • EEG features
  • Imaging findings
  • Examination findings
  • Cognitive/behavioural issues
  • Etc.

Current status of this system
  • No single specific organisation proposed for this
  • Individual epilepsy entities (regardless of
    specificity) should be organised as most relevant
    for the individual
  • May follow the same process used in 1989
    classification, or a completely different set of
    criteria depending on their fitness for purpose
    e.g. according to specific underlying cause or

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  • New proposed classification is recognised to be
    an evolutionary process
  • Several specific changes e.g. related to seizure
    classification, electro-clinical syndromes
  • No designated system for organising the
    classification clinicians will need to
    determine most appropriate structure for
    individual patients
  • Current classification reflects current state of
  • No change to the list of recognised epilepsies