Stereoelectroencephalography (sEEG) Versus Grids and Strips

Surgery has become an important therapeutic modality in the treatment of refractory epilepsy. Although noninvasive modalities remain the first-line tool for localization of a seizure onset zone, these data alone will be insufficient to enable precise localization of onset in some patients. The development of long-term invasive monitoring with subdural electrodes (SDEs) and stereoelectroencephalography (sEEG) has increased the number of patients eligible for surgical treatment by providing high-resolution electroencephalography recording that would be otherwise unavailable using scalp electrodes. Both forms of intracranial monitoring have their relative strengths and weaknesses, but their efficacy with respect to seizure localization has been well documented. SDEs are placed along the surface of the brain and are well suited to targeting ictal onset found in close proximity to eloquent cortex. Implantation requires a large craniotomy and the placement of a significant amount of intracranial hardware, which carries the risk of hemorrhage, infection, and cerebrospinal fluid leak, to name a few. sEEG is better suited to deep-seated lesions, recurrent or refractory seizures after prior surgery, and any patient in whom bilateral implantation is desired. Adverse events associated with sEEG are similar to those of SDEs but are encountered at a significantly lower rate. Neither intracranial recording modality is a universal solution for anyone with refractory epilepsy. Rather, the optimal tool to localize seizure onset should be a patient-specific decision based on their epilepsy history, the potential seizure foci identified during noninvasive evaluation, and an evaluation of how to best achieve that goal while minimizing risk.