Seizure Semiology and Classification
Dr Tim Wehner
NHNN
Epilepsy Daycourse
Royal Free Hospital, London
14 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
Symptom
Localisation
Specificity
Frequency*
Forced head turn (“version“)
Contralateral
>90%
35-40%
Unilateral dystonic posturing
Contralateral
>90%
20-35%
“Figure of Four“
Contralateral
90%
65% (sGTCS)
Postictal nosewiping
Ipsilateral
>70%
10-50%
Ictal speech**
Nondominant
>80%
10-20%
Ictal automatisms with
preserved awareness
Nondominant
100%
5%
(Post)ictal dysphasia
Dominant
>80%
20%
*In patients referred for presurgical video telemetry
Less common lateralising or localising
seizure manifestations
Symptom
Localisation
Specificity
Frequency
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 Seizures
Tonic-clonic (in any combination)
Absence
- Typical
- Atypical
- Absence with special features
Myoclonic absence
Eyelid myoclonia
Myoclonic
Seizure types thought to
- Myoclonic
occur within and result from
- Myoclonic atonic
rapid engagement of
- Myoclonic tonic
bilaterally distributed systems
Clonic
Tonic
Atonic
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, 2011
Lüders et al, Epilepsia, 53:405–11, 2012
Berg & Scheffer Epilepsia, 52:1058–62, 2011
Shorvon Epilepsia, 52:1052–57, 2011
• Glossary Blume et al, Epilepsia 2001