Microscopic cortical dysplasia in infantile spasms: evolution of white matter abnormalities.

PURPOSE To determine whether microscopic cortical lamination defects in patients with infantile spasms, not initially identifiable on MR, may be inferred from evolving changes in the adjacent white matter. METHODS Three infants between 3 and 6 months of age presented with infantile spasms. Based on negative metabolic assessment and normal MR findings, they were classified as cryptogenic. Despite therapy the children deteriorated with seizure recurrence and the advent of lateralizing clinical and neurophysiologic findings. MR studies were repeated and positron emission tomography was done. RESULTS The second MR studies demonstrated abnormalities of myelination, corresponding to localized clinical and neurophysiologic findings. Positron emission tomography findings did not show a strong correlation; one was normal, one showed no abnormality in the major area of MR abnormality, and one showed significantly less abnormality than on MR. Two patients have undergone surgery, both with good response. DISCUSSION Subtle lamination defects may be identifiable on positron emission tomography but are usually not detectable on MR. White matter abnormality on MR images is usually attributable to primary disease. We suggest that in certain cases progressive white matter changes may be induced as a secondary phenomenon by overlying microscopic cortical lamination defects. Serial MR imaging may be beneficial in children with infantile spasms in whom signs of laterality evolve.