1. ILAE Classification of Epilepsy - update
Chris Rittey
Sheffield

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

3. 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

4. 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

5. Changes

6. 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

7. 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

8. 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

9. 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

10. 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

11. I. Classification of seizures
GENERALISED 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
FOCAL SEIZURES
MAY BE FOCAL, GENERALISED, OR UNCLEAR
Epileptic spasms

12. 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”

13. 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

14. Syndromes will no longer be characterised as being focal or generalised

15. Classification ‘groups’
Electroclinical syndromes
Epilepsy constellations
Epilepsies secondary to specific structural or metabolic lesions or conditions
Epilepsies of unknown cause

16. 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

17. 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

18. 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

19. 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”

20. 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

21. 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

22. 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)

23. 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

24. 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).

25. 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.

26. 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)

27. 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

28. 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)

29. 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

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

31. 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

34. 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