Subdural recording in epilepsy

Abstract

It is the cortices and the cortico-cortical connections that are involved in manifestation of normal cortical functions as well as production of seizure symptoms. In this sense, presurgical evaluation of patients with intractable partial epilepsy helps us delineate cortical functions and networks at the individual level. In return, the advancement of clinical system neuroscience brought us better understanding and evaluation of clinical epileptology. Advancements of the digital EEG system enabled direct recording of neural activities with wideband electrocorticogram (ECoG). Wideband ECoG recording provided a comprehensive approach to probe epileptogenicity by combining both low (slow shift) and high (spontaneous and induced high gamma oscillations) ends of frequencies. Electrical cortical stimulation in epilepsy surgery can delineate the cortex responsible for a particular task by making transient focal functional impairment, which is in sharp contrast to chronic stroke lesions that are relatively large and usually associated with cortical plastic compensation. Cortico-cortical evoked potential (CCEP) is a recently developed, in vivo electrical tract tracing method for presurgical evaluation. It promises to refine our understanding of surgical candidacy, first through a more precise and tailored evaluation of the seizure network in each individual patient, and second through greater understanding of the functional systems of the brain involved, such as language and praxis. We introduce comprehensive mapping of these higher functions by combining the state-of-art system neuroscience methods, such as a modified quantitative method for high frequency electrical cortical stimulation, ECoG signal analysis and decoding, and CCEP.