<unk>  is caused by disruption to development of the fetal brain between the 3rd and 12th weeks of pregnancy. In most cases, it is not possible to know what caused an individual to have<unk>  or another callosal disorder. However, research suggests that some possible causes may include chromosome errors, inherited genetic factors, prenatal infections or injuries, prenatal toxic exposures, structural blockage by cysts or other brain abnormalities and metabolic disorders. Ciliopathies: rare genetic disorders Until recently, the medical literature did not indicate a connection among many genetic disorders, both genetic syndromes and genetic diseases, that are now being found to be related. As a result of new genetic research, some of these are, in fact, highly related in their root cause despite the widely varying symptoms apparent on clinical examination.<unk>  is one such disease, part of an emerging class of diseases called ciliopathies. The underlying cause may be a dysfunctional molecular mechanism in the primary cilia structures of the cell organelles that are present in many cellular types throughout the human body. The cilia defects adversely affect "numerous critical developmental signaling pathways" essential to cellular development and thus offer a plausible hypothesis for the often multi-symptom nature of a large set of syndromes and diseases. Known ciliopathies include primary ciliary dyskinesia, Bardet–Biedl syndrome, polycystic kidney and liver disease, nephronophthisis, Alström syndrome, Meckel–Gruber syndrome and some forms of retinal degeneration. Cocaine and other street drugs In utero exposure to cocaine, heroin, amphetamines and phenylpropanolamine can lead to<unk>  of<unk><unk> .
Agenesis of the corpus callosum
Germinal matrix hemorrhage
Congenital bilateral perisylvian syndrome
Cerebellar agenesis
Gray matter heterotopia
Bilateral frontoparietal polymicrogyria
Cerebellar hypoplasia
Pontocerebellar hypoplasia