Heterotopia is a sign of altered migration leading to an abnormal distribution of gray matter nodular masses with disorganized or rudimentary lamination within the periventricular area (periventricular heterotopia) or subcortical white matter (subcortical heterotopia) [2]. In the examined cohorts, heterotopias were detected in the brains of four autistic subjects and in the brain of one control subject. Heterotopias are associated with mutations in the filamin 1 gene (FLNA1) [39, 46] and the chromosome X-linked DCX gene that codes for doublecortin, a protein expressed during brain development in migrating neurons, and in the cortical plate [29, 44, 45], which is involved in the formation of the microtubules necessary for neuronal migration [15]. Periventricular nodular heterotopia has been reported to be associated with pharmaco-resistant seizures in 80–90% of patients [31]. In the examined cohort, two periventricular heterotopias were detected in the brain of a child with subependymal nodular dysplasia and seizures diagnosed at 14 months of age (B-6403). Early onset epilepsy, diagnosed at the age of 4.5 months, might be related to the multiple heterotopias found within the frontal inferior gyrus, vermis and cerebellar white matter, coexisting with a focal cortical dysplasia and dentate gyrus dysplasia (B-5342).
