Seizure Semiology and ClassificationDr Tim Wehner
NHNNEpilepsy Daycourse
Royal Free Hospital, London14 Feb 2014
Summary 1• Seizure semiology is an expression of activation
and disinhibition of cerebral areas• It thus provides some information what cerebral
areas are “involved” during a seizure• Video EEG provides objective data on seizure
semiology, however for most seizures in most patients information on semiology comes from patient’s and witness’ history
• Seizure classification aims to intellectually organise and summarise information about seizure semiology
Summary 2
• Seizure classification currently intensily debated in ILAE
• Relative consensus exists for seizure types seen in primary generalised epilepsies
• ILAE recognizes need to update classification of focal seizures, however no consensus in sight
• Why is it important – because we have nothing else to go by.
Take home messages
• Using obsolete or imprecisely defined terms is of little help
• Using defined terms inappropriately is even worse (“absence”)
• Patients and relatives should be encouraged to describe what they experience / see during a seizure without using terms such as “aura”, “petit mal”, “grand mal”, “simple partial”, “complex partial”, “deja vu” , “blackout”
www.ilae.org
Main changes, modifications• Language and structure for organizing epilepsies
– Generalized versus Focal Seizures– “Etiology”– Diagnostic specificity– New recommended terms– Organization
• NO changes to electroclinical syndromes– A diagnosis can be made as previously
eg Lennox-Gastaut syndrome, childhood absence epilepsy– A diagnosis is not the same as a classification
www.ilae.org
Focal reconceptualized• For seizures:
– Focal epileptic seizures are conceptualized as originating within networks limited to one hemisphere. These may be discretely localized or more widely distributed.…
www.ilae.org
Focal seizures Blume et al, Epilepsia 2001
• Without impairment of consciousness or awareness– Previous term: simple partial– With observable motor or autonomic components
• eg. focal clonic, autonomic, hemiconvulsive– With subjective sensory or psychic phenomena
• Aura - specific types
• Where alteration of cognition is major feature– Previous term: complex partial– Dyscognitive
• Evolving to bilateral, convulsive seizure– Previous terms: partial seizure secondarily generalized;
secondarily generalized tonic-clonic seizure– With tonic, clonic or tonic and clonic components
www.ilae.org
Symptomatogenic areas Left hemisphere, lateral aspect
Symptomatogenic areas Left hemisphere, mesial aspect
Symptomatogenic areas Left Insula
Common lateralising seizure manifestations
SymptomSymptom LocalisationLocalisation SpecificitySpecificity Frequency*Frequency*
Forced head turn (“version“)Forced head turn (“version“) ContralateralContralateral >90%>90% 35-40%35-40%
Unilateral dystonic posturingUnilateral dystonic posturing ContralateralContralateral >90%>90% 20-35%20-35%
““Figure of Four“Figure of Four“ ContralateralContralateral 90%90% 65% (sGTCS)65% (sGTCS)
Postictal nosewipingPostictal nosewiping IpsilateralIpsilateral >70%>70% 10-50%10-50%
Ictal speech**Ictal speech** NondominantNondominant >80%>80% 10-20%10-20%
Ictal automatisms with Ictal automatisms with preserved awarenesspreserved awareness
NondominantNondominant 100%100% 5%5%
(Post)ictal dysphasia(Post)ictal dysphasia DominantDominant >80%>80% 20%20%
*In patients referred for presurgical video telemetry
Less common lateralising or localising seizure manifestations
SymptomSymptom LocalisationLocalisation SpecificitySpecificity FrequencyFrequency
Elementary visual aura Contralateral occipital >90% ?
Acoustic aura Temporal, if unilateral then contralateral
>90% ?
Olfactory aura Mesiotemporal >70% ?
Abdominal aura
Automotor sz
Temporal
Temporal
90%
98%
Common
Ictal aphasia Dominant >80% ?
Ictal nystagmus contralateral >95% ?
Hyperkinetic movements
Frontal/frontomesial >80% >10%
Generalized - reconceptualized
• For seizures– Generalized epileptic
seizures are conceptualized as originating at some point within, and rapidly engaging, bilaterally distributed networks. …can include cortical and subcortical structures, but not necessarily include the entire cortex.
www.ilae.org
Generalized SeizuresTonic-clonic (in any combination)Absence
- Typical - Atypical - Absence with special features
Myoclonic absence Eyelid myocloniaMyoclonic
- Myoclonic- Myoclonic atonic- Myoclonic tonic
ClonicTonic Atonic
Seizure types thought to occur within and result from
rapid engagement of bilaterally distributed systems
www.ilae.org
Recommended terminology for etiology
Use terms which mean what they say:• Genetic• Structural-Metabolic • Unknown
Previously used terms denoting old concepts:Idiopathic, cryptogenic, symptomatic
www.ilae.org
Genetic
• Concept: the epilepsy is the direct result of a known or inferred genetic defect(s). Seizures are the core symptom of the disorder.
• Evidence: Specific molecular genetic studies (well replicated) or evidence from appropriately designed family studies.
• Genetic does not exclude the possibility of environmental factors contributing
www.ilae.org
Structural-Metabolic
• Concept: There is a distinct other structural or metabolic condition or disease present.– eg. Tuberous sclerosis
• Evidence: Must have demonstrated a substantially increased risk of developing epilepsy in association with the condition.
www.ilae.org
Unknown
• Concept: The nature of the underlying cause is as yet unknown.
www.ilae.org
New recommended terminology
Previously used terms no longer preferred• Classification as focal or generalized epilepsies
– not always appropriate– use when appropriate
• Catastrophic - emotionally laden term• Benign - does not recognize that co-morbidities occur, this
term is still used in syndrome names Recommended terms• Self-limited: high likelihood of spontaneous remission• Pharmacoresponsive
www.ilae.org
How to classify?• Absence• Aura• Dyscognitive sz• No seizure
• Absence is narrowly defined as a seizure with loss of awareness, sudden on- and offset, no postictal state, and 3Hz Spike and Wave complexes in the EEG
Elements of a seizure
• Subjective experience of the patient• Motor and behavioural manifestations• Awareness, language and cognition• Autonomic manifestations• May coexist in any combination, even in brief
seizures, and are a function of how well the patient is assessed during the seizure
Key References
• ILAE commission report, www.ilae.org• Comments by
Panayiotopoulos Epilepsia, 52:2155-60, 2011Lüders et al, Epilepsia, 53:405–11, 2012Berg & Scheffer Epilepsia, 52:1058–62, 2011Shorvon Epilepsia, 52:1052–57, 2011
• Glossary Blume et al, Epilepsia 2001