Postprocessing of Structural MRI in the Presurgical Evaluation of Epilepsy Patients Digitale Nachverarbeitung von strukturellen MRI- Aufnahmen in der prächirurgischen Diagnostik von Epilepsiepatienten

Summary Using the example case of a former patient as a guiding line, the article gives an overview of several novel methods of computer-assisted MRI postprocessing and their clinical application in non-invasive and invasive presurgical evaluations of epilepsy patients. Morphometric MRI analysis facilitates the detection and delineation of subtle focal cortical dysplasias and other cortical malformations by highlighting typical structural alterations like thickening of the cortical ribbon, blurring of the grey-white matter junction, and abnormal gyration. Automatic curvilinear reformatting of 3D MRI data calculates serial convex planes across the brain in different depths from the cortical surface. This method improves the display of the gyral structure, permits a precise localization of lesions, and helps to identify subtle abnormalities difficult to detect in planar slices. Pre-operative planning of subdural electrode implantation for invasive EEG recordings by means of realistic 3D representation of electrode contacts is a novel method that allows calculating electrode positions directly on the convexity of the individual cortical surface and in correct spatial proportions with respect to brain size. Thereby it permits rapid and exact determination of optimal electrode positions and supports planning and execution of electrode implantation. After implantation, the positions of subdural electrodes can be determined by help of an automated fast method for volume rendering of 3D MRI at the level of the implanted electrodes. The results of all presented methods can be integrated into intra-operative neuronavigation systems to support final lesion resection. After surgery, coregistration of pre- and postoperative images makes it possible to confirm the completeness of lesion resection. In conclusion, a variety of MRI postprocessing methods aids in the presurgical evaluation and surgical management of medically refractory epilepsy patients. Epileptologie 2013; 30: 90 – 100