O156 A functional connectivity analysis of patients with temporal lobe epilepsy with different propagation patterns

Objective To analyze the functional connectivity (FC) of temporal lobe and related areas in patients with temporal lobe epilepsy (TLE) showing unilateral lateralized ictal discharges (uniTLE) and unusual ictal propagation patterns (UiP) defined as ‘switch-of lateralization’ and ‘bilateral asynchrony’ in scalp EEG. Methods Twelve TLE patients with UiP (6 with left and 6 with right seizure-onset) and 13 patients with uniTLE (7 with left and 6 with right seizure-onset) and 13 healthy controls (HC) underwent resting state functional MRI. ROI-to-ROI FC analyses were carried out between homologous insula, hippocampi, parahippocampal gyri, amygdala, superior temporal and middle temporal gyri. Results All TLE patients showed reduced overall FC compared to HC, where univariate comparisons revealed that the connectivities were significantly reduced between right and left insula, parahippocampal and superior temporal gyri. MANOVA among the 3 groups revealed that the uniTLE patients displayed a lower FC between the homologous parahippocampal gyri, while patients with UiP had lower FC between the homologous insula, parahippocampal and superior temporal gyri when compared with the HC. Furthermore, TLE patients with UiP showed significantly lower FC between the bilateral insula when compared with uniTLE patients. Discussion While the reduction level of the resting-state FC between the homologous temporal lobe structures may depend on neural loss, a network change to protect contralateral temporal areas might also play role in further reduced FC in TLE with UiP. This might support the presence of independent epileptogenic zones bilaterally rather than a propagation from the contralateral hemisphere.