In the examined brains of autistic subjects, signs of neuronal immaturity were a common finding. Failure of maturation of neuronal precursors caused by altered expression of cytoskeletal proteins and loss of neuronal polarity results in defects in migration to the destined layer and in incorrect vertical and horizontal orientation [93]. The immaturity of dysplastic neurons is reflected in the expression of a variety of proteins and mRNA that are not present in mature neurons an altered expression of developmentally regulated cytoskeletal elements [3, 23, 61, 76], which are known to be crucial for dendrite arborization, spine formation, axon outgrowth and maintenance of cell size and shape. Reduced cell size, dendritic arborization and spine expression are characteristic of dysplastic neurons [6, 93]. Cortical dysplasias are the most epileptogenic lesions of the brain [107] and are observed in up to 25% of all epileptic surgeries [102]. More subtle cortical malformations or dysgenesis encountered in adults with epilepsy may lack the histological criteria for focal cortical dysplasia. They have been described as mild cortical dysplasia or microdysgenesis [77].
