THE DEMONSTRATION OF GYRAL ABNORMALITIES IN PATIENTS WITH CRYPTOGENICPARTIAL EPILEPSY USING 3-DIMENSIONAL MRI

Background: Despite the use of high-resolution magnetic resonance imag ing (MRI) in the demonstration of structural abnormalities underlying chronic partial epilepsy, a significant proportion of MRI scans in suc h cases still appear normal when viewed conventionally as two-dimensio nal images, especially in extratemporal epilepsies. Objectives: To inc rease the yield of MRI in patients with extratemporal epilepsies. To e xamine specific regions of three-dimensional surface renderings of the cerebral hemispheres. Design: Postprocessing of volumetric MRI data w as used to detect abnormalities of gyration that may not be seen other wise. Setting: Scans were obtained at a hospital clinical imaging faci lity. Participants: Sixty-four subjects were studied: 33 controls, 15 patients with hippocampal sclerosis (as disease controls), and 16 pati ents with cryptogenic partial epilepsy that on clinical grounds was ex tratemporal. Main Outcome Measures: Gyral patterns were evaluated for abnormality by visual comparison between subjects. Results: Inspection of the routine two-dimensional images had failed to demonstrate relev ant underlying neocortical abnormality in any of the patients' scans. Three-dimensional reconstruction revealed abnormal gyral patterns in t he frontal lobe convexity in seven of the 16 cryptogenic clinically ex tratemporal cases. Macrogyria was revealed in one case and increased g yral complexity with altered disposition was seen in six cases. Simila r gyral patterns were not seen in any subjects from the other groups. Conclusion: Three-dimensional analysis of volumetric MRI data can reve al structural abnormality that is not visible when the data are viewed as two-dimensional images only.