Epilepsy Surgery or ECOG (Electrocorticography)
Goal: prescribe an anesthetic plan that avoids ECOG suppression. ECOG is used to locate the source of epileptic foci while preserving functional cortex.
These cases may necessitate awake craniotomy with intraoperative ECOG and functional mapping or general anesthesia with ECOG +/- MEPs. You will need to discuss the plan with the neurosurgeon ahead of time for proper planning.
Benzodiazepines suppress interictal epileptiform discharges (IEAs) and should be avoided.
Conscious sedation or an Asleep-Awake-Asleep may be used with the following drugs:
Infusion and/or boluses for skull pinning and scalp infiltration
Infusion for maintenance but stop infusion 20 minutes before ECoG
Has the least effect on IEAs
Loading dose followed by infusion
Stop or decrease infusion during ECoG
Fentanyl (bolus or infusion) or remifentanil infusion
May continue low dose infusion of remifentanil during ECoG
Inhaled drugs- for asleep technique after testing is complete
Avoid other drugs that cause sedation like antihistamines
Warn patients preoperatively about risk of awareness during ECoG.
IV induction including opioids
Maintenance with TIVA or low dose (.5 MAC) inhaled drugs (Sevoflurane or Isoflurane)
Nitrous Oxide may diminish IEAs if used with other inhaled agents but not if used with opioid technique.
Beware inhalational anesthetics if surgical plan involves Motor Mapping (MEP) which are very sensitive to inhalational agents and muscle relaxants
Both IV and inhaled drugs are weaned down or stopped.
Low dose REMI or dexmeditomidine may be continued.
Muscle relaxant may be needed to prevent movement and pharmacological activation may be needed to enhance IEAs. Etomidate is probably the easiest choice at 6-14 mg. bolus if surgeon requests.
For your reference: “The Anesthetic Considerations of Intraoperative Electrocorticography during Epilepsy Surgery” Anesthesia-Analgesia. 4/2013