Anesthesia for Epilepsy Surgery

🔹 Introduction

Epilepsy affects over 50 million people globally, and about 30% are refractory to medical therapy. In select cases, surgical intervention becomes necessary to remove or disconnect epileptogenic foci. These surgeries can be curative or palliative, and anesthesia plays a crucial role in balancing seizure detection, neurophysiological monitoring, and hemodynamic control.


🔹 Types of Epilepsy Surgeries

Procedure Type

Example

Curative (resective)

Temporal lobectomy, lesionectomy, cortical resection

Functional (disconnective)

Corpus callosotomy, hemispherectomy

Diagnostic/Monitoring

Intracranial electrode placement (grids, strips, SEEG)

Palliative

Vagus nerve stimulator (VNS), deep brain stimulation (DBS)



🔹 Anesthetic Goals

  1. Maintain optimal conditions for seizure localization
  2. Preserve neurophysiological monitoring (ECoG, MEPs, SSEPs)
  3. Ensure patient safety, including airway protection and hemodynamic stability
  4. Provide rapid recovery for awake testing (in awake craniotomy cases)
  5. Avoid interference with seizure activity detection


🔹 Preoperative Considerations

🔸 Neurological Evaluation

  • Identify seizure type (e.g., focal, generalized, temporal lobe)
  • EEG/MRI/PET/SPECT localization of seizure focus
  • History of status epilepticus or medication-refractory seizures

🔸 Antiepileptic Drugs (AEDs)

  • Most patients are on multiple AEDs (e.g., phenytoin, valproate, levetiracetam)
  • Continue AEDs preoperatively to avoid breakthrough seizures
  • Enzyme-inducing AEDs affect anesthetic drug metabolism (e.g., phenytoin → ↓ propofol, opioids)

🔸 Airway Assessment

  • Prolonged AED use → gingival hyperplasia, osteomalacia
  • Some may have cognitive deficits or behavior issues


🔹 Intraoperative Management

🔸 Monitoring

Standard

Invasive/Advanced

ECG, SpOâ‚‚, EtCOâ‚‚, NIBP

Arterial line (if blood loss risk), Foley catheter

EEG/ECoG

For seizure focus localization

MEP/SSEP

If motor pathways involved

BIS

If TIVA used (controversial in presence of seizures)



🔸 Induction

  • IV induction with propofol, etomidate, or thiopentone
  • Short-acting opioids (remifentanil/fentanyl)
  • Rocuronium or atracurium if paralysis needed

Avoid benzodiazepines if seizure detection is required.


🔸 Maintenance

Agent

Role

TIVA (Propofol + Remifentanil)

Preferred for stable neurophysiology

Volatile agents (Sevo, Des)

Acceptable in non-mapping phases, but may suppress epileptiform discharges

Avoid Nâ‚‚O

May increase CBF and ICP, may promote seizure activity

No muscle relaxant

During ECoG or motor mapping to preserve responses



🔸 Intraoperative Seizure Management

Cause

Management

Cortical stimulation, spontaneous seizure

Suction cold saline, stop stimulation

Drug-related (e.g., LA toxicity)

Airway control, benzodiazepines, intralipid if LAST suspected



🔹 Special Considerations

🧠 Awake Craniotomy for Epilepsy Surgery

Used especially for language mapping in dominant hemisphere (usually left temporal lobe)

Requirement

Details

Patient selection

Cooperative, no cognitive impairment

Anesthesia technique

Asleep–awake–asleep or Monitored anesthesia care (MAC)

Drugs

Dexmedetomidine, remifentanil, propofol (carefully titrated)

Challenges

Airway control, anxiety, patient movement


🧠 Electrocorticography (ECoG)

  • Performed intraoperatively after dura opening
  • Helps identify epileptogenic zones
  • Propofol and volatile agents suppress ECoG signals
  • Minimize or avoid these during mapping


🔹 Vagus Nerve Stimulator (VNS) Surgery

  • Electrode wrapped around left vagus nerve
  • Generator implanted subcutaneously (chest wall)
  • Watch for bradycardia during manipulation
  • May cause hoarseness, cough, or apnea


🔹 Postoperative Considerations

Issue

Management

Seizures

Resume AEDs early, maintain serum levels

Neurological deficit

Early imaging if new focal signs

Airway issues

Especially in VNS/awake craniotomy

Pain control

Paracetamol, opioids (cautious with sedation)

Nausea/vomiting

Ondansetron, dexamethasone (if not contraindicated)



🔹 Viva Points and FAQs

  • Why TIVA preferred? → Preserves neurophysiological signals better than volatiles.
  • Why avoid benzos? → Suppress EEG activity, interfere with seizure detection.
  • Which inhaled agent lowers seizure threshold? → Enflurane (no longer used).
  • Drugs that provoke seizures intra-op? → Ketamine, etomidate, meperidine (theoretically).
  • Why use cold saline irrigation? → Terminate intraoperative seizure safely.
  • Why left vagus nerve for VNS? → Right vagus has more cardiac fibers → bradycardia risk.


📚 Summary Table

Parameter

Epilepsy Surgery

Anesthetic Technique

TIVA preferred

Seizure Monitoring

EEG, ECoG, avoid CNS depressants

Airway

Nasal/oral ETT; awake craniotomy may need LMA or face mask

AEDs

Continue perioperatively

Muscle relaxant

Avoid during ECoG

Postop

Seizure control, early neuro eval



🧠 Suggested Readings

  • Miller’s Anesthesia, 9th Edition
  • Cottrell and Young’s Neuroanesthesia
  • BJA Education: Neuroanesthesia for Epilepsy
  • StatPearls: Epilepsy Surgery and Anesthesia