What is the differential diagnosis for what appears to be massively dilated ventricles on a prenatal ultrasonography (US) or MRI examination?
The appearance of massively dilated ventricles may be secondary to holoprosencephaly, hydranencephaly, or hydrocephalus. Hydranencephaly results from massive necrosis of the cerebral hemispheres and may be secondary to vascular disease with bilateral internal carotid occlusion, infection, or trauma. In contrast to hydranencephaly, there is a thin residual remnant of cerebral cortex applied to the inner table of the calvaria seen with severe hydrocephalus. The most common causes of prenatal hydrocephalus include Arnold-Chiari malformation II, intracranial hemorrhage, aqueductal stenosis, and Dandy-Walker malformation.