Intracranial electrophysiological explorations for medically refractory partial epilepsy.

During the past 20 years, advances in neuroimaging techniques have greatly improved the surgery of epilepsy. Nevertheless, for fifty percent of epileptic patients undergoing such surgery procedures, recordings with chronically implanted intracerebral electrodes are necessary to localize the epileptic focus. Since the fifties, these electrodes have been used to record the cerebral cortex during the surgical procedure. Due to technological progress, these electrodes can now be left implanted for several days to record the inter- and per-ictal electroencephalogram (EEG). In comparison with scalp recordings, intracortical assessment of epileptic patients allows exploring the cortical epileptic network with a higher spatial resolution and less artefacts. Moreover, this technique enables performing direct cortical electrical stimulation to map functionally eloquent cortices and epileptogenic areas. Each type of depth electrodes has been developed for a specific use. In this work, we review the different solutions used at the present time, their specific indications and finally their advantages and disadvantages. Moreover, we mention the new emerging therapeutic indications.