Brain activity during intraoperative general anesthesia using resting-state functional magnetic resonance imaging ~Feasibility study~

Electroencephalogram (EEG) monitors are widely used to evaluate depth of anesthesia. However, EEG monitors have problems such as differences in evaluation depending on the type of anesthetic and influences from drugs other than anesthetic agents. Monitoring of brain activity using intraoperative resting-state functional MRI (rs-fMRI) would be expected to improve evaluation of the depth of anesthesia in EEG monitoring. We examined the feasibility of evaluating the effects of general anesthesia with sevoflurane using rs-fMRI during neurosurgery. We enrolled 20 adult patients scheduled for transsphenoidal surgery. We compared differences between before and during general anesthesia in terms of brain functional connectivity of the thalamus by seed-to-voxel correlation analysis and local neural activity using fractional amplitude of low-frequency fluctuations (fALFF) analysis. An exclusion mask was applied to exclude brain areas showing intraoperative spatial artifacts and correct for differences in the magnitude of intra- and preoperative head movements. We analyzed 16 patients. Functional connectivity of the thalamus to the contralateral thalamus, bilateral caudate nuclei and globi pallidi was significantly decreased during anesthesia. The precuneus and posterior cingulate cortex showed significantly decreased fALFF values during anesthesia. These findings were consistent with previous studies and indicate the feasibility of intraoperative rs-fMRI during deep anesthesia.