Abstracts

Rationale: Pathogenesis and origin of reflex-eating epilepsy is incompletely understood. There are no studies using MEG and exploring source localisation and coherence analysis in these patients. Methods: Analysis of 306 channels MEG recording in five patients (M: F=2:3; age: 24 ± 4.9 years) with intractable reflex-eating and spontaneous partial epilepsy was done. Interictal discharges (IED) at conventional bandwidth (0.3-70 HZ) were identified. Source localisation was performed on boundary element head model (6*8*9 mm tessellations) using s-LORETA (standardized low resolution electromagnetic tomography). During the IEDs, sensor coherence was performed at threshold of 80-90%, considering a time lag of 1-2.5 milliseconds; source coherence was attempted using CDR currents in 3D segmented cortex of the brain (MRI) using CURRY software. Results: All five patients had frequent IEDs. Source localisation of IEDs performed at dipolar topographical pattern was at peri-sylvian cortex -3; temporal -1; and parieto-occipital cortex-1. Intra-hemispheric sensor coherence was more than inter-hemispheric sensor coherence during the IEDs in all five patients. Directionality of coherence was more from anterior to posterior direction- 4; posterior to anterior direction in 1; and superior to inferior direction in all 5 patients. Significant source coherence was observed in three patients during a time lag of 10-40 milliseconds when the direction of propagation was identified: lateral temporal lobe and peri-sylvian regions to posterior parieto-occipital lobe in 1 patient each and parieto-occipital lobe to temporal lobe in 1 patient. Conclusions: This is the first MEG study, which identified the cortical source of origin and propagation of spikes in patients with reflex-eating epilepsy. Majority patients might have probable source of trigger near the peri-sylvian region with propagation to either lateral temporal cortex or to parieto-occipital cortex. Coherent MEG sensors corresponded with the region of source localisation. The observation is in agreement with studies using EEG.