Abstracts

Mesial temporal lobe epilepsy (MTLE) due to mesial temporal sclerosis (MTS) is a unique clinical syndrome, which may produce specific ictal perfusion patterns. To investigate this possibility, we compare a group of patients with MTLE due to MTS with a group of patients with MTLE due to other etiologies. We retrospectively reviewed consecutive intractable partial epilepsy patients who had ictal and interictal SPECT images performed at Saint Louis University Hospital. Patients with video-EEG recordings and MRI findings consistent with seizures of mesial temporal lobe onset were included in the series. We recorded the time sequence of all seizure semiology and injection of radiotracer. Subjects were determined to have MTS using MRI-based hippocampal volumetric asymmetery and/or post-operative pathological results. Using a previously validated technique, we created composite SISCOM images of the MTS and non-MTS groups. To compare all subjects, the subjects with right-sided onset of seizures were inverted, so that perfusion changes are depicted on the left side of the final template composite images. There were 17 subjects in the MTS group, and 14 subjects in the non-MTS group. For the MTS group, mean seizure duration was 90 s, and mean injection time was 32 s. For the non MTS group, mean seizure duration was 96 s, and mean injection time was 34 s. Regions of perfusion significance were set at P[le]0.012 for the MTS group, and P[le]0.016 for the non-MTS group. A gradient shading scale was then used to show the regions of significant perfusion change for the MTS and non-MTS groups. Figure 1 shows the perfusion changes of the MTS group (left image) and non-MTS group (right image). The middle image is the coregistered template MRI. Cross-hairs show the same reference in space of all images. The regions of perfusion changes were similar between the two groups, showing the anterior temporal region, basal ganglia, and insula as the most commonly perfused regions in both groups.[figure1] Regional hyperperfusion patterns in MTLE due to MTS are similar to hyperperfusion patterns of seizures of medial temporal onset due to other etiologies. This is suggestive that activation of neuronal networks in seizures of medial temporal onset is more dependant on neuro-anatomical localization of seizure onset than the underlying neuropatholocial etiology of the epileptic seizures.