[Intraoperative Monitoring of epileptic foci: usefulness of multimodality image-guided epilepsy surgery performed in combination with electrocorticography].

Intraoperative monitoring for epilepsy surgery is an important technique for ensuring accurate focus resection. This paper reviews the usefulness of multimodality image-guided epilepsy surgery and intraoperative electrocorticography (ECoG) with regard to intraoperative monitoring of epileptic foci. The development of modern modalities such as magnetic resonance imaging (MRI), positron emission tomography (PET), single-photon emission computed tomography (SPECT), magnetoencephalography (MEG), and electroencephalography (EEGs) has ensured that surgeons can now detect focus areas with great accuracy before commencing surgery. Furthermore, the use of a multimodality image-guided system ensures that the same information can be used during surgery and enables surgeons to accurately define the boundaries of epileptic foci determined by various preoperative tests. In addition to the preoperative data, more data regarding epileptic foci can be obtained during intraoperative ECoG. Although the clinical role of ECoG remains uncertain, several studies have revealed the potential usefulness of techniques such as hippocampal ECoG and ECoG performed for confirming the completeness after multiple subpial transections, and so on. Our group used a combination of multimodality image-guided epilepsy surgery and intraoperative ECoG for patients with MRI-visible lesions; the surgeries were performed under general anesthesia. Of the 14 patients followed-up for at least 3 years after surgery, 13 archived an Engel Class I outcome. This paper also briefly introduces an intraoperative intrinsic optical recording technique for determining the precise functional distributions in the sensory cortex in order to avoid postoperative neurological deficit.