Distinct brain network structure of mesial temporal lobe epilepsy compared to that of neocortical epilepsy: functional MRI study with surgically treated patients

OBJECTIVE Mesial temporal lobe epilepsy (mTLE) and neocortical epilepsy (NE) have different anatomo-clinical characteristics. The authors hypothesized that this may be reflected in the different functional connectivity of the epileptogenic zone between mTLE and NE. The authors, therefore, examined preoperative resting-state functional connectivity MRI with regional global connectivity (rGC) analysis for surgically treated patients. The goal of this study was to detect the different functional networks associated with the epileptogenic zone between mTLE and NE. METHODS Twenty-four patients (12 with mTLE and 12 with NE) who underwent surgery were included in the study. All patients received resting-state functional MRI preoperatively. The mean rGC and number of high-rGC or low-rGC voxels were calculated using preoperative MRI in various regions of interest including the resected area. RESULTS The ratio of mean rGC in the resected area to that of the whole brain was significantly lower in mTLE patients than in NE patients. Mean rGC was significantly lower than that of the contralateral counterpart of the resected area in mTLE patients, although it was not significantly different in NE patients. Low rGC was more frequently observed in the resected area in mTLE patients than NE patients, and high rGC more frequently observed in NE than mTLE. Multivariate analysis showed that the etiology of hippocampal sclerosis, the ratio of mean rGC in the resected area to that in the whole brain, and the ratio of the number of low- and high-rGC voxels relative to the whole brain were significant factors to distinguish mTLE from NE. CONCLUSIONS The authors revealed a distinct brain network structure between mTLE and NE based on rGC analysis with resting-state functional MRI. The authors’ unique functional connectivity analysis may be helpful for providing landmarks for lateralization or epileptogenic zones in mTLE and NE.