Which condition is described by destruction of the cerebral cortex due to vascular compromise or congenital infection, with brain tissue replaced by CSF?

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

Answer: (A)

This description points to hydranencephaly. It’s a severe destructive process in which the cerebral hemispheres are essentially destroyed, usually from a profound vascular insult (often bilateral internal carotid artery compromise) or a congenital infection. When this happens, the brain tissue of the hemispheres is replaced by cerebrospinal fluid, leaving the skull and brainstem structures intact. The result is a fluid-filled cranium with little or no cerebral cortex, while the brainstem and cerebellum are typically preserved.

On imaging or prenatal ultrasound, you’d see near-total absence of the cerebral hemispheres with fluid occupying the space they would normally fill, and the falx may still be present. This helps distinguish it from other conditions: an arachnoid cyst is a localized CSF-filled space within the arachnoid membrane, not a widespread loss of cortical tissue; Dandy-Walker malformation involves the posterior fossa with an enlarged fourth ventricle and cerebellar vermis hypoplasia; acrania is the absence of the skull with exposed neural tissue. Hydranencephaly uniquely features destruction of the cerebral cortex with CSF replacement, while the other conditions involve different structures or localized processes.