Cortical Dysplasia and Heterotopias

Abstract

The use of magnetic resonance (MR) imaging has revolutionised our ability to detect small areas of dysplastic grey matter in the cerebral cortex, hemispheric white matter and subependymal regions. Although large areas of dysplastic cortex and grey matter heterotopia were recognised by computed tomography (CT) and, for that matter, pneumoencephalography, the results of subtle derangements of normal neuronal migration have only recently been detected (Barkovich et al, 1987, 1989; Barth, 1987; Smith et al., 1988; Byrd et al., 1989; Kuzniecky et al, 1989; Palmini et al., 1991a,b,c,d; Barkovich and Kjos, 1992a,b,c). In fact, distinctions between the various categories of neuronal migration anomalies are losing their meaning as a result of the knowledge that we have gained through analysis of MR images. For example, band heterotopias (double cortex) seem to be part of a continuum between grey matter heterotopias and type I lissencephaly (Palmini et al., 1991a). Large subcortical heterotopias may, in fact, be deep involuted areas of cortical dysplasia (Barkovich and Kjos, 1992a).