Patients with frequent interictal spikes (> 3/20 min) underwent EEG-MREG and EEG-EPI (3 T, 20 min each, voxel size 3 脳 3 脳 3 mm, EPI TR = 2.61 s, MREG TR = 0.1 s). Timings of the spikes were used in an event-related analysis to generate activation maps of t-statistics. (FMRISTAT, |t| > 3.5, cluster size: 7 voxels, p < 0.05 corrected). For both sequences, the amplitude and location of significant BOLD activations were compared with the spike topography.
13 patients were recorded and 33 different spike types could be analyzed. Peak T-values were significantly higher in MREG than in EPI (p < 0.0001). Positive BOLD effects correlating with the spike topography were found in 8/29 spike types using the EPI and in 22/33 spikes types using the MREG sequence. Negative BOLD responses in the default mode network could be observed in 3/29 spike types with the EPI and in 19/33 with the MREG sequence. With the latter method, BOLD changes were observed even when few spikes occurred during the investigation.
Simultaneous EEG-MREG thus is possible with good EEG quality and shows higher sensitivity in regard to the localization of spike-related BOLD responses than EEG-EPI. The development of new methods of analysis for this sequence such as modeling of physiological noise, temporal analysis of the BOLD signal and defining appropriate thresholds is required to fully profit from its high temporal resolution.