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