Iniencephaly: a neuropathologic study.

Five cases of iniencephaly are reviewed. Numerous central nervous system malformations were found at all levels, including microencephaly, polymicrogyria, heterotopic glial tissue in the leptomeninges, atresia of the ventricular system, marked disorganization of the brain stem, vermian agenesis, large cerebellar cyst, and disorganization of the spinal cord tissue. The cerebellum was normal in one case. Numerous skeletal anomalies were found as well as marked retroflexion of the craniocervical junction. We concluded that cerebral anomalies, although severe, are not specific for iniencephaly. Cerebellar anomalies, on the other hand, were considered to share some morphologic features between Dandy-Walker and Arnold-Chiari, i.e., Chiari type II and Chiari type III, malformations.