Epileptogenic Zone
“Area of cortex that is necessary and sufficient for initiating seizures and whose removal (or disconnection) is necessary for complete abolition of seizures”
Hans Lüders, 1993
History
1884-1935 (Sir John Hughlings Jackson & Victor Horseley)
-1st cortical resections for EPI
-Szs originate from a specific cortical region that can be surgically targeted
Early–Mid 20th Century: Penfield & Jasper
-ECoG to map, now epileptic activity can be recorded & localized
1966: Tailarach & Bancaud
-sEEG based definition
1993: Lüders
-EZ, hypothetical concept
2000s–present
-Focal view to network model
Concepts
EZ
-Minimum amount of cortex to achieve SF
-Inferered it by combining multiple zones
-Minimum amount of cortex to achieve SF
-Inferered it by combining multiple zones
Seizure onset zone (SOZ)
-Szs is actually generated as measured by EEG
Ictal onset zone (IOZ)
-Szs actually begin, as recorded on sEEG
>Often smaller than the EZ
>Sometimes only part of true epileptogenic network
>Sometimes only part of true epileptogenic network
Potential ictal onset zone
-Might be involved in szs onset but are not definitively proven due to limited data
>Common in sEEG when sampling is incomplete
-Might be involved in szs onset but are not definitively proven due to limited data
>Common in sEEG when sampling is incomplete
Irritative zone
-Generates interictal epileptiform discharges as defined by EEG
-Generates interictal epileptiform discharges as defined by EEG
>Usually larger than true EZ
>Helps guide electrode placement but is not sufficient for surgical targeting
Epileptic lesion zone
-Structural abnormality seen on neuroimaging believed to be source of szs
>Not all lesions are epileptogenic, and some EZs occur without visible lesions
Early spread zone
-Region involved immediately after szs onset
>Helps distinguish primary onset from rapid spread
>Spread zones are not necessarily part of EZ
>Spread zones are not necessarily part of EZ
Symptomatogenic zone
-Activation produces clinical sx of szs
>Sx often reflect spread, not onset
>Not removed if overlaping essential function
Eloquent cortex
-Damage causes major, permanent deficits
>Avoid resecting, unless absolutely necessary
Non-eloquent cortex
-Resection is less likely to cause major functional impairment
>Most resections target this area
-Resection is less likely to cause major functional impairment
>Most resections target this area
Putative epileptogenic zone (Resection margins)
-Estimated EZ based on all available data
-Estimated EZ based on all available data
-Area planed to be removed
-Practical, clinically actionable version of theoretical EZ
-Practical, clinically actionable version of theoretical EZ