An 11-month-old boy with refractory epilepsy: Answer

Abstract

The patient’s MRI (Fig. 1 of Images in Neuroscience: Question) shows right hemispheric lissencephaly of the temporo-parietooccipital region with frontal sparing (long arrows). There is associated right subcortical band heterotopia (arrowheads in A and B) and focal left sided subependymal nodular heterotopias (short arrows in A and B). Lissencephaly and the related malformation, subcortical band heterotopia, are classical neuronal migration defects [1]. Lissencephaly denotes a smooth brain with areas of absent and abnormally wide gyri (agyria and pachygyria, respectively), whereas subcortical band heterotopia indicates a double cortex condition [2]. The most common clinical presentation is epilepsy followed by global developmental delay, early infantile hypotonia, feeding difficulty and ophisthotonus [3]. Brain MRI displays a spectrum which varies from agyria (grade 1 and 2) to pachygyria (grade 3 and 4) to normal convolutions separated by narrow sulci overlying a heterotopia. In most patients a gradient exists between anterior and posterior regions. They may have associated corpus callosum and cerebellar hypoplasia. Recognition of these patterns enables focused molecular diagnosis, prognostication and estimation of genetic risk. To our knowledge, six associated genes have been described: LIS 1 (posterior predominance), DCX (anterior predominance), RELN and VLDLR (anterior predominant lissencephaly