Hydranencephaly - a rare congenital brain malformation

Hydranencephaly is a rare brain malformation in which there is near total absence of

cerebral hemispheres. The child may appear normal at birth but usually has a large

head. The diagnosis is established by CT or MRI and there is no known treatment.

In this case we can see that CSF attenuation fills supratentorial cranial vault with intact falx cerebri and thinned out brain parenchyma around the falx with absent/ indetectable brain parenchyma around bilateral lateral cranial vault. Thin line of cortical mantle noted in bilateral temporal and inferior frontal lobe region.

The thalamus appears to be intact though the remaining deep white matter could not be seen. Posterior fossa appears to be intact and remnants of cerebral cortex in the frontal lobe could be made out.

Discussion :

Hydranencephaly is In-utero cerebral hemispheric destruction with preservation of thalamus, brainstem (BS), cerebellum

The term is taken from "hydrocephalus" + "anencephaly"

Hydrancephaly is one of the rare but devastating congenital malformations of the brain consisting of nearly complete absence of both cerebral hemispheres.The exact aetiology of the

abnormality is still unknown but is believed to be a significant vascular insult in the territories

of both internal carotid arteries after the fourth month of gestation, so that the portion of the

brain supplied by the anterior and middle cerebral arteries is replaced by cerebrospinal fluid. The patient has a normal cerebellum and brainstem supplied by the vertebrobasilar system. The cranium is intact and there is a well formed and somewhat thickened sac consisting of an outer leptomeningeal layer and rudimentary representation of cortex.

CT Imaging findings are :

o CSF attenuation fills supratentorial cranial vault

o Falx cerebri partially/completely intact, basal ganglia separated

Differential Diagnoses for this condition are :

Severe hydrocephalus

Alobar holoprosencephaly

Severe bilateral schizencephaly

Cystic encephalomalacia