Abstracts

Rationale: Intracranial EEG (icEEG) is one of the most important diagnostic tools in presurgical evaluation in epileptic surgery patients. Traditional interpretation of icEEG, however, is often difficult. Visual analysis of EEG waveforms in over 100 channels may not be analyzed the same way by different reviewers. Also, 3D localization of ictal onset zones is challenging based on 2D data. This study aimed to develop a new approach to visualize icEEG using a 3D movie display of EEG power on the brain surface and to validate its clinical usefulness for seizure localization.Methods: We selected 49 intractable epilepsy patients who underwent icEEG recordings and epilepsy surgery between 2004 and 2010 with at least one year of postsurgical follow-up. There were 27 temporal and 22 extratemporal lobe epilepsy patients. The first three seizures for each patient were reviewed and analyzed. First, we selected patients with good surgical outcome and reviewed the seizure onset zones unblinded to test the technique for displaying icEEG power on the 3D brain surface. BioImage Suite (v3.0, CT, USA, www.bioimagesuite.org) was used to render a 3D triangular mesh surface from MRI, and Matlab (2010a, Mathworks, MA, USA) was used to calculate icEEG power of different frequency bands (delta, theta, alpha, beta, gamma) and to make a 3D color movie. Each face of the triangular mesh surface assumed the color of the closest electrode, and a linear fade of the transparency was applied over 15 mm of each electrode. Using conventional visual analysis, two independent reviewers interpreted ictal icEEG recordings to localize seizure onset zones blinded to any clinical information. The same reviewers separately interpreted seizure onset zones from 3D movie display of icEEG power in different frequency bands.Results: Based on conventional visual analysis, the overall agreement rates between two reviewers were 97.2%, 75.2%, and 61.4% for seizure lateralization, lobar, and sublobar brain regions, respectively. 3D color movie display was helpful to more rapidly and accurately localize the seizure onset zones, and was generally in agreement with conventional visual analysis.Conclusions: These findings suggest that 3D color movie display may be a useful diagnostic technique for presurgical seizure localization.