Ependymoblastomatous exencephaly: a unique fetal malformation.

Exencephaly/anencephaly is a rare neural tube defect occurring early in embryogenesis. We report a 14-week-old fetus with exencephaly in whom central nervous system tissue was developed and preserved. There were 2 symmetrical structures grossly resembling cerebral hemispheres, which on histologic and ultrastructural study, consisted of a combination of ependymoblastomatous rosettes and canals and primitive neural tissue. The brainstem and spinal cord were partially normally formed, although descending tracts were not apparent. No cerebellar tissue was found. The eyes were formed. This appears to represent a rare example of exencephaly not covered by skin, which did not undergo necrosis and early transformation into a residual area cerebrovasculosa, characteristic of anencephaly. It may be appropriate to regard this as a unique neural tube closure defect that might be termed "ependymoblastomatous exencephaly."