Abstracts

Rationale: EEG-fMRI has been used to map ictal networks; BOLD patterns consistently include decreases in areas spatially distant from the seizure onset zone[1]. A recent development has been the simultaneous recording of intracranial-EEG and fMRI (icEEG-fMRI)[2], which has demonstrated significant interictal epileptiform discharge (IED)-related BOLD changes in all cases studied to date. Here we report on a patient who had a focal electrographic seizure during icEEG-fMRI.Methods: A 30y.o. male underwent intracranial-EEG recordings as part of presurgical evaluation for refractory focal temporal lobe epilepsy. We used a strict safety protocol [2], and gained informed written consent for the icEEG-fMRI study. He was selected because he had an electrographic seizure during icEEG-fMRI recording. He underwent left anterior temporal lobe resection and has ILAE Class I postsurgical outcome at 3 years. We constructed two models of the seizure: 1. A visually derived model using 30s pre-ictal, ictal onset and late-ictal phase as in [1]. 2. An unbiased model of spectral dynamics was calculated by taking the channel of earliest visual change, transforming into the time-frequency domain, taking a z-score and convolving by the canonical heamodynamic response function before being reduced using principle component analysis (PCA). The PCAs explaining >90% variance were then used as a model of ictal dynamics (fig. 1). The fMRI data was analyzed using each of the two seizure models (with motion and cardiac confounds) in SPM8 (www.fil.ion.ucl.ac.uk).Results: One electrographic seizure with two distinct phases: ictal-onset phase and late-ictal phase, was recorded. Ictal-onset consisted of fast (beta) activity involving right mesial temporal contacts duration = 6.4sec. Late ictal phase was fast (gamma) activity in right and left mesial temporal contacts, duration 14.8s (fig. 2). Preictal changes were distributed bilaterally as small clusters of biphasic BOLD responses. For ictal-onset, BOLD increases were seen in right medial basal temporal, inferior temporal gyrus and precuneus; and BOLD decreases in right superior temporal gyrus, medial temporal pole, medial superior frontal gyrus and posterior cingulate. For late-ictal phase, BOLD increases were seen in precuneus, posterior cingulate, left temporal pole; BOLD decreases in left inferior temporal gyrus; biphasic BOLD changes in right middle frontal gyrus (fig. 2). The PCA model from right amygdale showed BOLD changes in the right sensori-motor cortex, middle temporal gyrus, posterior temporal and amygdale, medial occipital; on the left BOLD changes were found in the superior parietal lobe and posterior hippocampus (fig. 1).Conclusions: We have recorded the first sub-clinical seizure with simultaneous intracranial EEG and fMRI. We used two modeling approaches using either neurophysiologically meaningful features or an unbiased representation of spectral dynamics. Both seizure models found BOLD changes in a network containing nodes around the onset zone and also in other cortical and deeper structures. 1. Chaudhary U, et al, Brain, 2012, Dec;p3645-63 2. Carmichael DW, et al, Neuroimage, 2012, Oct;p301-9