Abstracts

Detection of abnormalities in neuroimaging studies greatly enhance the chances of surgical success in patients with refractory epilepsy. We evaluated the use of diffusion MRI (DW) performed in the early postictal period (defined as less then 2 hours) after a focal seizure and to compare the findings with ictal SPECT. We studied a consecutive series of patients who had a focal seizure documented by video-EEG monitoring, during which a ⁹⁹ⁿTc-ECD was injected to obtain ictal SPECT images. Before SPECT imaging, patients were taken to the MRI scanner, where whole brain (24 five milimeter slices) rapid DW acquisitions were obtained on a 1,5T Ge scanner (GE Medical Systems), with single shot echo planar sequences, using a 128X128 matrix, a TE=114 and fov 26 cm. The sequence was applied in the three orthogonal planes, with a b+ 1000s/mm² in each direction. DW-MRI results were interpreted by three independent neuroradiologists. Results were compared with those of ictal SPECT, ictal EEG and structural brain MRI. Six consecutive patients with focal epilepsy were studied (4 symptomatic: hippocampal sclerosis in 2, tuberous sclerosis in 1, focal cortical dysplasia in 1 and cryptogenic in 2: frontal and temporal), with ages ranging from 7 to 55 years. DW-MRI was performed in all cases less than two hours after the video-EEG documented focal seizure, during which ⁹⁹ⁿTc-ECD was injected to obtain ictal SPECT. No abnormalities were seen on DW images in any of the cases. On the contrary, ictal SPECT showed increased flow, concordant with neuroimaging or ictal EEG in 5 cases, and, in the remaining case, increased blood flow was noted in the cerebellum, in the opposite side of the lesion. This preliminary study did not detect abnormalities on DW-MRI performed in the early postictal period (less than two hours) of focal seizures, while ictal SPECT showed increased flow in all cases (regionalizing in 5 and lateralizing in the remaining case).