Insult during neuronal migration results in delayed neuroneal migration and organization, which results in ceain disorders. The least likely possibility is:

Formation & maturation of brain neocoex involve neuronal proliferation, differentiation & migration. With their expansion, germinal matrix forms at 7 weeks gestational age d/t subependymal neuronal proliferation, lines the lateral & third ventricles and involutes at 28 to 30 weeks With the exception of outer layer, neurons migrate from germinal matrix to coex in an inside out sequence: i.e. those that will form the deepest coical layer (6) migrate first, followed by layers 5, 4, 3 and finally layer 2 (layer 1 will not migrate). This neuronal migration & layering process occurs from weeks 6 to 7 through 24 to 26, when full 6 layered coex is achieved. So a brain insult during neuronal migration can result in abnormalities ranging from lissencephaly (smooth brain), to schizencephaly (split brain), polymicrogyria, and laminar or focal heterotopiasQ.