Hydraencephaly
Hydraencephaly is a severe brain defect (Figure 293.6). The cerebral hemispheres are replaced by a membranous cyst consisting of a thick pia-glia membrane. Hydraencephaly is due to occlusion of the supraclinoid portion of the internal carotid artery in utero with progressive cerebral infarction. Skull transillumination is usually present except if the fluid is bloody or contains high protein levels. These neonates may look and act normal during the first weeks of life although usually have difficulty feeding and hypothermia. Macrocephaly is not always present.

A	B	C

Figure 293.6— Hydraencephaly. [A] Clinical appearence. [B] MRI, transverse view. [C] MRI, sagittal view.