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 strataI. Classification of seizures

II. Syndromes and epilepsies

III. Aetiological designation

IV. Other dimensions

IV-A. Age at onset

IV-B. Natural evolution

IV-C. Other features

I. Classification of seizuresGENERALISED SEIZURESTonic clonic (in any combination)

Absence - typical

- atypical

- absence with special

features

- myoclonic absence

- eyelid myoclonia

Myoclonic - myoclonic

- myoclonic atonic

- myoclonic tonic

Clonic

Tonic

Atonic

FOCAL SEIZURES

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 epilepsiesEpilepsies attributed to and organized by structural-metabolic causes

Malformations of Cortical development (hemimeganencephaly, hetertopias etc)Neurocutaneous syndromes (Tuberous sclerosis complex, Sturge-Weber, etc)TumorInfectionTraumaAngiomaPeri-natal insultsStrokeEtc.

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 dimensionsIV-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 dimensionsIV-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 dimensionsIV-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