The demonstration of gyral abnormalities in patients with cryptogenic partial epilepsy using three-dimensional MRI
S. M. Sisodiya, J. M. Stevens, D. R. Fish, S. L. Free and S. D. Shorvon
Epilepsy Research Group, Institute of Neurology, London, England.
BACKGROUND: Despite the use of high-resolution magnetic resonance imaging
(MRI) in the demonstration of structural abnormalities underlying chronic
partial epilepsy, a significant proportion of MRI scans in such cases still
appear normal when viewed conventionally as two-dimensional images,
especially in extratemporal epilepsies. OBJECTIVES: To increase the yield
of MRI in patients with extratemporal epilepsies. To examine specific
regions of three-dimensional surface renderings of the cerebral
hemispheres. DESIGN: Postprocessing of volumetric MRI data was used to
detect abnormalities of gyration that may not be seen otherwise. SETTING:
Scans were obtained at a hospital clinical imaging facility. PARTICIPANTS:
Sixty-four subjects were studied: 33 controls, 15 patients with hippocampal
sclerosis (as disease controls), and 16 patients with cryptogenic partial
epilepsy that on clinical grounds was extratemporal. 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 relevant underlying neocortical abnormality in any of
the patients' scans. Three-dimensional reconstruction revealed abnormal
gyral patterns in the frontal lobe convexity in seven of the 16 cryptogenic
clinically extratemporal cases. Macrogyria was revealed in one case and
increased gyral complexity with altered disposition was seen in six cases.
Similar gyral patterns were not seen in any subjects from the other groups.
CONCLUSION: Three-dimensional analysis of volumetric MRI data can reveal
structural abnormality that is not visible when the data are viewed as
two-dimensional images only.