Intracranial Electro Corticogram(ECOG) is an invasive EEG monitoring using subdural grids/strips or depth electrodes. Depth electrodes are an excellent modality designed to study electrical discharges from deep grey matter.
Placement of these electrodes needs general anaesthesia. Once the electrodes are inserted, the patient can have a further period of telemetry.
With this information, the seizure focus can be defined with greater accuracy and it is also possible to undertake functional mapping of the cortical areas studied.
During resective epilepsy surgery intraoperative ECOG helps to guide the resection.
☀️Propofol is the commonly used induction agent
☀️nitrous oxide : controversial (?decreases the spike activity significantly in some studies)
☀️remifentanil infusion enhances spike activity in the epileptogenic zone. So it can be used during ECOG monitoring
☀️Sevoflurane has greater neuro excitatory properties than isoflurane, however, the wide spread irritative response to sevoflurane is not useful in localizing the epileptogenic area. Therefore it may not be suitable for ECOG monitoring during surgery.
☀️Patients who are on long term treatment with phenytoin and carbamazepine may have increased fentanyl requirements and may be resistant to non- depolarising relaxants.
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