NeuroradiologyHydranencephaly
the result of an early destructive process involving the developing brain; the causes may be different, including toxoplasmosis and cytomegalovirus, but an arterial occlusive
vascular mechanism involving the carotid arteries is a suggested cause.
The cortex and white matter are completely destroyed and replaced by thin-walled sacs mainly made of leptomeningeal connective tissue, containing CSF. The thalami are usually preserved as well as sometimes the mesial aspects of the temporal lobes and the inferior medial aspects of the frontal lobes.
The children may be microcephalic but CSF circulation may be impaired and severe dilatation of the head results. Differential diagnosis with severe hydrocephalus may be difficult if the remaining rim of cortex and white matter is too thin.
The children's development is usually severely retarded and shunting does not improve the condition.
Complete absence of the cerebral hemispheres, replaced by CSF, with the exception of thalami is best shown on MR.
GS