Intraoperative magnetic resonance imaging in epilepsy surgery.

The aim of this study was to investigate how intraoperative magnetic resonance imaging (MRI) can help in epilepsy surgery to asses immediately whether a resection or disconnection procedure is tailored to the individual needs of a patient, thus ideally meeting the treatment plan and enhancing the efficiency of the procedure. The recently proposed concept of an individually tailored procedure with as limited tissue removal as possible would support a more conservative resection than initially advocated by many centers; such limited removal would preserve as much brain as possible that is not necessarily epileptogenic or involved in propagation of seizures. For intraoperative imaging we used a Magnetom Open 0.2-T scanner located in our "twin-OR" in 61 patients with pharmacoresistant epilepsy. A three-dimensional sequence was used, allowing free slice reformatting. In the nonlesional cases (n = 32) the extent of the tailored temporal resection (n = 28) or callosotomy (n = 4) could be documented exactly. In the 29 lesional cases the complete resection was primarily proved in 23 patients. In three glioma patients a lesion that extended into eloquent areas did not allow for complete removal. A second look (n = 3) could increase the rate of total resection in the lesional cases from 79% to 90%. Intraoperative MRI allowed a reliable evaluation of the extent of resection or disconnection in epilepsy surgery within the operative procedure. It also provided the possibility of a second look in cases of incomplete resection, especially in the lesional cases. Increased knowledge of structure-function relationships as partially defined by intraoperative imaging may reduce the adverse neuropsychological sequelae of epilepsy surgery in the future.