Noninvasive Multimodal Neuroimaging for Rasmussen Encephalopathy Surgery: Simultaneous EEG-fMRI Recording

Rasmussen syndrome is characterized by continuous partial seizures with progressive neurological/cognitive impairment. Currently the only effective treatment is surgery (hemispherectomy). The objective of our study is to detect the exact epileptogenic focus through the analysis of multimodal noninvasive and innocuous functional neuroimaging.

The subject is a 5-year-old female patient with Rasmussen encephalopathy. Continuous and simultaneous electroencephalography-functional magnetic resonance imaging (EEG-fMRI) was record ed. The sources of background and paroxysmal activity of EEG were computed by low resolution electromagnetic tomography (LORETA). Image analysis (SPM: statistic parametric mapping) was obtained for the areas where statistically significant differences in the fMRI BOLD response were computed, and the results from both techniques were compared.

The main source of paroxysmal activity by EEG analysis was found in the anterolateral left hemisphere, with a significant increase in absolute and relative energies of slow frequency bands (theta-delta): Z ≥ 3. The fMRI BOLD signal (basal vs. paroxysmal activity) was significantly different in the same region (t-test ≥ 2.39). The generators of propagated paroxysmal activity were found in similar areas for both techniques.

In conclusion, simultaneous EEG-fMRI recording allows the analysis of two harmless functional neuroimaging techniques separately and together in the same time period. In our case, it allowed the accurate delineation of epileptogenic foci and areas of spread with high spatiotemporal resolution, which is crucial for epilepsy surgery.