“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
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
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
Irritative zone -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
Symptomatogenic zone -Activation produces clinical sx of szs >Sx often reflect spread, not onset >Not removed if overlaping essential function
4) Piccolo player, dystonic flexion of the left third finger at the middle phalanx (pattern IId)
*Botox at the flexor digitorum superficialis of 3
5) Pianist, extension of 3 and flexion of 4 and 5
6) Violinist, flexion of 4 (likely lumbrical-mediated)
7) Flexion of the 3rd finger (likely lumbrical-mediated) (pattern IIf)
8) Extension of 4 and 5
9) Jazz guitarist, flexion of 5 (pattern IIi)
G3 - Precision
1) Flexion/adduction of the thumb and extension of 2 while playing (pattern IIIa)
2) Flexion/adduction of the thumb and flexion of 2 while writing, producing a pincer-like posture of the thumb and index finger holding the pen (pattern IIIb)
3) Flexion of the thumb (particularly the distal phalanx) while playing (pattern IIIc)
4) Hybrid banjo/guitar, extension of the thumb and flexion/adduction of 2 while playing (pattern IIId)
5) Banjo player, dystonic extension of the thumb while playing (pattern IIIe)
G4 - Proximal
1) Pianist, isolated extension of the wrist as soon as his left hand touches the keyboard (pattern Va)
2) Guitarist, pronation of the wrist, which spread to the task of writing (pattern Vb)
3) Tennis coach, wrist flexion dystonia which spread to occur when he held his arms up (pattern Vc)
4) Percussionist, ulnar deviation of the left wrist while playing with “soft mallets” in a fast roll (pattern Vd)
5) Violinist, subtle loss of vibrato 2/2 biceps activation (VIa)
6) Violinist, dystonia of the bow arm (pattern VII)
*Botox injection
7) Athletics, dystonia of the throwing arm causes the ball to fly wildly off target (pattern EA)
Scales
-Tubiana & Chamagne Scale
Pathophysiology
-Maladaptive sensorimotor plasticity
-Power hand mismatch→ hand is evolutionarily designed to stabilize and exert force onto an object, rather than engaging in precision kinetics
Observations
-Manipulandum DTN→ instrument-specific
-Overflow DTN→ spread to adjacent muscles
-Can progress from focal→ segmental DTN
>Initially task‑specific, but may lose task specificity
-High spread risk in woodwind players (speech/swallowing involvement)
Differential Dx
-Overuse syndromes
-Entrapment neuropathies (e.g., ulnar neuropathy)
>Neuropathy may coexist but is rarely the primary cause
