Abstracts

Rationale: Intracerebral recordings have suggested alterations of hippocampal networks in temporal lobe epilepsy (TLE). We evaluated the hippocampal networks in TLE non-invasively using resting state functional MRI (fMRI) connectivity analysis, a technique that analyzes hemodynamic coherence of a seed area and maps the underlying associated network. Methods: Regions of interest were identified in both the left and right hippocampi to be used as seeds to develop coherence maps in resting state MRIs of 5 subjects with right TLE (R-TLE), 5 with left TLE (L-TLE), and 6 control subjects. Pair-wise tests were done between the 3 groups separately for each seed analysis. The coherence maps were compared by a whole-brain independent t-test, and corrected for multiple comparisons by cluster correction (z > 2.3, p < 0.05). Analyses used FSL (FMRIB s Software Library, Oxford University, UK). Results: Compared to controls, patients with R-TLE and L-TLE demonstrated decreased left hippocampal connectivity to bilateral medial occipital areas and the precuneus, and increased right hippocampal connectivity to the periventricular white matter. Comparison between R-TLE and L-TLE did not show significant differences. Conclusions: A novel fMRI technique of investigating functional networks in TLE demonstrated reduced connectivity of the left hippocampus to occipital networks and increased connectivity of the right hippocampus to periventricular white matter. These changes were similar in both L-TLE and R-TLE suggesting that these network-level changes are likely a function of the disease (TLE) and not based on lateralization.