Which of the following statements is correct regarding the disorder Subcortical band heteropia?
ExplanationThe disorder depicted is subcortical band heterotopia, a malformation of cortical development, more specifically a neuronal migration disorder (not a disorder of cortical organization). The lissencephaly syndromes result from neuronal migration abnormalities and include subcortical band heterotopia, or double cortex, in which there is relatively normal cortex (with six layers) with an underlying band of white matter, underneath which is a band of gray matter . This disorder results from a mutation in the DCX gene on chromosome X in females. DCX encodes for the protein doublecortin, which is involved in microtubule organization and stabilization. The same mutation can lead to classic lissencephaly (smooth brain, agyria, or pachygyria) when occurring in males. This difference in manifestations in females as compared with males is thought to result from lyonization (random X inactivation) in females (XX), such that normal migration cannot occur in neurons in which the mutated gene is not compensated by the normal homologous copy, and neurons with normal copy of the gene can migrate to the cortex, resulting in a double cortical band. Subcortical band heterotopia can also occur in some patients with mosaic mutations of LIS1. Clinical features in patients with subcortical band heterotopia include intractable seizures, intellectual impairment and other neurologic deficits. ; it is characterized by agyria or pachygyria rather than the presence of two bands of gray matter separated by a band of white matter. Cobblestone lissencephaly (rather than subcortical band heterotopia), formerly known as lissencephaly type 2, is seen in several disorders, including Walker–Warburg syndrome, Fukuyama muscular dystrophy, and muscle–eye–brain disease of Santavuori . In polymicrogyria, there are excess, abnormal gyri
