Morphologic characteristics of subcortical heterotopia: MR imaging study.

BACKGROUND AND PURPOSE Gray matter heterotopia have been divided into three groups based on clinical and imaging characteristics: subependymal, subcortical, and band heterotopia. Nonetheless, subcortical heterotopia can have variable morphologic findings. The purpose of this study was to perform a morphologic analysis of a series of cases of subcortical heterotopia based on MR images, to correlate the morphologic appearance with clinical characteristics, and to speculate about the embryologic implications of our results. METHODS The MR imaging studies and clinical records of 24 patients with subcortical heterotopia were retrospectively reviewed. The morphologic findings of the heterotopia were recorded along with presence and type of associated malformations. These results were correlated with available data on development and neurologic status. RESULTS Analysis revealed that, in six cases, the heterotopia were composed exclusively of multiple nodules, in 13, they appeared primarily as curvilinear ribbons of cortex extending into the white matter, and in five, they had deep nodular regions with curvilinear areas more peripherally. All of the curvilinear regions were contiguous with the cerebral cortex in at least two locations. In eight cases, curvilinear heterotopia contained curvilinear areas of flow void that were thought to be blood vessels; in 10, they contained fluid resembling CSF. No difference in developmental or neurologic manifestations was noted among patients with heterotopia of different morphologic appearances. CONCLUSION Subcortical heterotopia can have nodular or curvilinear morphologic appearances. Although no difference was found in the clinical conditions of the patients with differing morphologic appearances, additional analysis of these patients or studies of animal models of these malformations may further our understanding of normal and abnormal brain development.