Overview

• Most common and best-studied epilepsy surgery worldwide
• Standard procedure for mesial temporal lobe epilepsy (mTLE) with hippocampal sclerosis
• Resects anterior temporal neocortex + mesial structures (amygdala, hippocampus, parahippocampal gyrus)

Resection Extent

• Dominant hemisphere: 3.5–4.5 cm from temporal pole
• Nondominant hemisphere: 5–6 cm from temporal pole
• Intraoperative ECoG may guide additional resection beyond standard limits

Outcomes

• Engel I at 1 year: 60–70% for mTLE with HS; 40–55% without HS
• Wiebe 2001 (NEJM): RCT — surgery 58% vs. medical 8% seizure-free at 1 year
• ERSET 2012 (JAMA): early surgery RCT — 73% vs. 0% seizure-free at 2 years
• NNT = 1.6 (Wiebe) — one of the largest treatment effects in clinical neurology

Complications

Key Points

• Targets only mesial structures (amygdala, hippocampus, parahippocampal gyrus) while preserving lateral temporal neocortex
• Engel I: 55–65% — may be slightly lower than standard ATL
• Cognitive advantage: better naming and verbal memory preservation, especially with transsylvian approach

Surgical Approaches

• Less tissue removed than ATL — may have slightly lower seizure-free rates
• Best for patients where cognitive preservation is a priority, especially dominant hemisphere

Overview

• MRI-guided stereotactic laser ablation via 3.2 mm burr hole
• Hospital stay: 1–2 days; return to work: 1–2 weeks
• Real-time MRI thermometry monitors ablation in real time

Outcomes for MTLE

• Engel I: 55–60% at 12 months
• SLATE trial (prospective multicenter, 114 treated): 58% Engel I at 12 months
• Lower seizure-freedom rate than ATL (60–70%) — trade-off for minimally invasive approach

Cognitive Advantages

• Better naming preservation than open ATL (spares lateral temporal neocortex)
• Better verbal memory outcomes for dominant-hemisphere surgery
• Particularly valuable for left-sided MTLE where cognitive risk is highest

Technical Keys & Pitfalls

• Most common cause of failure: incomplete hippocampal head ablation
• Target: 60–70% of hippocampus + most of amygdala
• Does NOT “burn bridges” — open ATL remains fully feasible after LITT failure
• Complications: hemorrhage ~1.5%, visual field defect 8.8%, transient CN III/IV palsy 3.1%

Hypothalamic Hamartoma

• 60–80% seizure-free with LITT in experienced centers
• First-line treatment at some centers for gelastic seizures from hypothalamic hamartoma
• Lower complication rates than open/endoscopic approaches for this deep-seated target

Predictors of Surgical Success

• Complete resection = single strongest predictor regardless of pathology
• Concordance between semiology, EEG, and MRI
• ECoG-guided extended resection for residual epileptiform activity
• Visible MRI lesion > MRI-negative for surgical planning and outcome

Indications

• Primary indication: disabling DROP ATTACKS (tonic, atonic seizures) refractory to medical therapy
• LGS is the most common indication
• Palliative procedure — does not cure epilepsy but reduces most disabling seizure type
• Not for focal resectable epilepsy; reserved for generalized or multifocal epilepsy

Procedure

• Staged approach preferred: anterior 2/3 callosotomy first; complete callosotomy if drop attacks persist
• Complete callosotomy more effective but higher risk of disconnection syndrome

Outcomes

• Eliminates drop seizures: 55% of patients
• Complete seizure freedom: 19%
• Better outcomes with: history of infantile spasms, shorter epilepsy duration, complete callosotomy

Disconnection Syndrome

• Alien hand syndrome: hand acts independently; more common with complete callosotomy
• Split-brain effects: interhemispheric transfer deficits — naming difficulty for objects in left hand, writing/reading deficits, bimanual coordination problems
• Transient postop deficits: leg weakness, akinesia, mutism from medial frontal retraction — usually resolve in days to weeks
• Risk higher with complete callosotomy → supports staged approach

Indications

• Rasmussen encephalitis: progressive unilateral encephalitis + epilepsia partialis continua — hemispherectomy is the definitive treatment
• Hemimegalencephaly: unilateral hemispheric enlargement with drug-resistant epilepsy
• Perinatal stroke: large unilateral infarction with resultant epilepsy
• Sturge-Weber syndrome: hemispheric leptomeningeal angiomatosis
• Candidates typically have preexisting contralateral hemiparesis

Procedure Types

• Anatomic hemispherectomy: complete hemisphere removal — historical; associated with superficial hemosiderosis and hydrocephalus
• Hemispherotomy (functional disconnection): preferred modern technique — disconnects hemisphere while preserving most cortex
• Techniques: vertical parasagittal, periinsular, endoscopic-assisted

Outcomes

• 73% seizure-free in children at last follow-up
• Better outcomes in younger children (greater neuroplasticity for functional reorganization)
• Adults have comparable Engel I rates when appropriately selected

Expected Deficits

• Contralateral hemiparesis: most patients already have preoperative hemiparesis; upper extremity typically more affected
• Homonymous hemianopia: expected and accepted
• Language: children with early-onset hemispheric pathology often have significant language reorganization to contralateral hemisphere
• Complications: hydrocephalus requiring shunt 10–20%, hemorrhage, aseptic meningitis

Frontal Lobe Epilepsy Surgery

• Engel I at 1 year: 30–50%
• Engel I at 5 years: only 28% — significantly worse than temporal resections
• Challenges: large epileptogenic zones, rapid seizure propagation, proximity to eloquent cortex, frequent MRI-negative cases
• SEEG is often required for bilateral frontal exploration

Parietal and Occipital Lobe Surgery

• Limited data; variable outcomes (50–65% for lesional cases)
• Parietal: risk of sensory deficits, apraxia, Gerstmann syndrome (dominant side)
• Occipital: contralateral hemianopia is expected if primary visual cortex is resected

Key Principle

• FCD IIb = best extratemporal surgical outcome (well-defined margins, transmantle sign on MRI)
• MRI-negative extratemporal epilepsy has the lowest surgical success rates

Late Recurrence

• Recurrence after initial 2-year seizure freedom occurs in 22–37% beyond 10 years
• Recurrent seizures are typically less frequent and less severe than preoperatively
• Late recurrence often manageable with ASM restart or medication adjustment
• Further surgical evaluation may identify treatable residual epileptogenic zone

Timeline

• Continue all preoperative ASMs for a minimum of 1–2 years after surgery
• Early postoperative seizures (first 1–2 weeks) = “running-down” seizures; do NOT necessarily predict surgical failure
• If seizure-free at 1–2 years: consider slow taper, one ASM at a time

ASM Withdrawal

• ~50% of patients eventually achieve complete ASM freedom after successful surgery
• Recurrence risk after complete withdrawal: 20–30%
• Predictors of safe withdrawal: Engel IA, normal postoperative EEG, lesional pathology (HS, tumor), absence of generalized discharges
• Decision must weigh medication side effects vs. recurrence risk (driving, employment, injury)