Destruction of the cerebral cortex resulting from vascular compromise or congenital infection, with brain tissue replaced by CSF and the brain stem spared, describes which condition?

• A. Hydranencephaly
• B. Arachnoid cyst
• C. Dandy-Walker
• D. Acrania

Answer: (A)

Hydranencephaly is a destructive process where the cerebral hemispheres are essentially destroyed, usually from a severe vascular event in utero or a congenital infection, and the brain tissue is replaced by cerebrospinal fluid. The result is an almost entirely fluid-filled cranial cavity with the brainstem and remaining midline structures preserved. In ultrasound imaging, you’d see the absence of the cerebral hemispheres while the brainstem, thalami, and basal structures remain intact, distinguishing it from other conditions.

This differs from an arachnoid cyst, which is a CSF-filled space within the arachnoid membrane that displaces but does not replace brain tissue. Dandy-Walker malformation involves defects in the posterior fossa with cerebellar vermis agenesis and enlargement of the fourth ventricle, not destruction of the cerebral cortex. Acrania involves failure of the skull bones to form over a partly developed brain, with brain tissue present rather than replaced by CSF.