Intraoperative electrocorticography in temporal lobe epilepsy surgery

Although in clinical use for many years, the validity of intraoperative ele ctrocorticography (ECoG) in guiding resective temporal lobe epilepsy (TLE) surgery is uncertain. Advances in neuroimaging and extraoperative intracran ial recordings have contributed greatly to the identification of epileptoge nic lesions and cortex, clarifying the limitations of a brief intraoperativ e interictal recording. Studies of undifferentiated ECoG findings (which cl assify all interictal cortical spike discharges as equal) tend to not suppo rt this method. This article reviews ECoG and presents data from 86 TLE sur geries at the University of British Columbia suggesting that differentiatio n of ECoG features may enhance the contribution of this time honored method . Specifically, independent foci may be more important for epileptogenesis than synchronous foci, and postexcision activation appears to be a benign p henomenon, while residual spikes unaltered by the resection correlate with a greater proportion of seizure recurrence.