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
2010
• 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
abandoned
• 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
Changes
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 distributed
• 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 simplified
• 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
concepts
• Myoclonic atonic (myoclonic astatic) seizures now
recognised
• Category of unclassified epileptic seizures no longer
accepted
Classification strata
I.
II.
III.
IV.
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
GENERALISED SEIZURES FOCAL SEIZURES
Tonic clonic (in any combination)
Absence - typical
- atypical
- absence with special
features
- myoclonic absence
- eyelid myoclonia
Myoclonic - myoclonic
- myoclonic atonic
- myoclonic tonic
Clonic
Tonic
Atonic
MAY BE FOCAL, GENERALISED,
OR UNCLEAR
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 seizure”
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 disorder
• 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 features
• 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. surgical
• Include:
• Temporal lobe epilepsy (with hippocampal sclerosis)
• Gelastic seizures with hypothalamic hamartoma
• Rasmussen syndrome
• Age at presentation is not a defining feature
Epilepsies secondary to specific lesions
or conditions
• 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 cryptogenic
• Account for 1/3 or more of all people with epilepsy
• 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 onset
• 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 structuralmetabolic 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 (< 44 weeks gestational age)
• Infant (< 2 years)
• Child (2-12 years)
• Adolescent (12-18 years)
• Adult (> 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
consequences
• 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
classification
• 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 lesion
Summary
• 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 knowledge
• No change to the list of recognised epilepsies