Abstracts

To investigate if multimodal imaging, including different new structural and functional imaging techniques, improves the detection of subtle structural lesions and helps define the seizure onset/irritative zone.
Fifty patients (pts) with medically intractable focal epilepsies were evaluated within their presurgical diagnostic workup using a standardized protocol including:
[italic]1. High-resolution 8-channel array surface coil MRI (3T) (SC-MRI): [/italic]Pt. were investigated with SC-MRI using a standardized protocol including T1, T2 and FLAIR sequences. An intensity normalization correction algorithm was used (Wald 1995). Images were analyzed by an experienced neuro-radiologist.
[italic]2. Whole head 306-channel MEG/64-channel EEG[/italic] was perfomed simultaneously in each pt. Spikes were analyzed calculating equivalent current dipoles using a boundary head element model for each spike. Dynamic statistic parametric maps (dSPM, Dale 2000) were calculated showing spike propagation with high spatiotemporal resolution.
[italic]3. High resolution Diffusion Tensor Imaging (DTI) at 3T[/italic]: DTI was acquired in each pt. Fractional Anisotropy (FA) maps were determined for each pt to evaluate differences in white matter (wm) microstructure between the affected and contralateral hemisphere. Data were used for tractography in some pt.
[italic]4. Cortical thickness and subcortical volumety and segmentation using semi-automated image analysis tools:[/italic] Automated software tools were used to calculate cortical thickness for each point of the cortex. Segmentation of subcortical gray matter was performed as described previously (Fischl [amp] Dale 2000, Fischl 2000).
All imaging techniques provided valuable information towards presurgical evaluation:
SC-MRI improved the detection of focal lesions and improved the specificity of the diagnosis in 18/50 pts (36%). In some cases SC-MRI improved the confidence in the MEG/EEG evaluation. Simultaneous MEG/EEG-evaluation detected MEG-only spikes in 16% (8/50 pt). dSPM improved the prediction of the size and location of the irritative zoneby showing propagation with high spatiotemporal resolution. TI detected more diffuse microstructural changes in the wm than suspected on either visual interpretation or by MEG/EEG. Automated analysis for Cortical thickness analysis detected more widespread cortical thickness changes than suspected on either visual interpretation or on MEG/EEG.
Combined multimodal imaging provides more information than any modality alone. This may improve selection of surgical candidates and improve predictions of postsurgical outcome. Further correlation with post-surgical outcomes is required.
[Supported by: Mind Institute, Förderverein Neurologie Univeristy Marburg, Germany, Prof. Dr. Adolf Schmidtmann Stiftung, Germany]