Intraoperative electrocorticography in epilepsy surgery: useful or not?

Intraoperative electrocorticography (ECoG) has been traditionally used in the surgical management of medically refractory partial epilepsies to identify the location and limits of the epileptogenic area, to guide the extent of resection, and to assess its completeness. Although in clinical use for many years, the basic questions regarding indications and limitations of this method has remained unanswered. ECoG plays a major role in tailored temporal lobectomies, whereas, it serves no practical purpose in standard resection of medial temporal lobe epilepsy (TLE) with magnetic resonance imaging (MRI) evidence of mesial temporal sclerosis (MTS). Residual hippocampal spikes, unaltered by resection, correlate with a greater proportion of seizure recurrence. Intraoperative hippocampal ECoG can allow sparing of functionally important hippocampus, thus minimising postoperative memory decline. ECoG eminently aids removal of developmental malformations of brain, and most importantly, the excision of highly epileptogenic cortical dysplasias (CDs) for deciding the extent of resection for best seizure control. The ECoG can be a valuable tool during multiple subpial transections (MST).