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Neuro - Neuroimaging and Pathology Coorelations

Terms in this set (106)

Hydranencephaly is a congenital brain defect in which fluid-filled cavities replace the cerebral hemispheres. It appears to be the result of either massive brain infarction from bilateral carotid artery occlusion or from primary agenesis of the neural wall. The cerebellum, midbrain, thalami, and basal ganglia are usually preserved.

The cerebral hemispheres are initially echogenic in hemorrhagic areas, becoming cystic as the brain becomes necrotic. The amount of cerebral cortex decreases over time and is replaced with fluid and debris. Eventually no cerebral cortex is visible. Sonographic findings may include macrocephaly and a large fluid filled intracranial cavity with variable amount of echogenicity, representing liquified brain and blood. One group described the appearance of the intracranial contents as uniform low-level echogenicity similar to endometrioma fluid.

If hydranencephaly occurs early, it may result in a small head/microcephaly. No cerebral cortex is present anteriorly, but there may be partial preservation of portions of the occipital lobe and the midbrain and the basal ganglia are variably preserved. Polyhydramnios is usually present by the end of the second trimester since the brain abnormality leads to poor fetal swallowing. However, fetal movement, including breathing and sucking motions, is preserved.

As discussed above, both alobar holoprosencephaly and hydranencephaly are characterized by absence of the midline echo; however, in hydranencephaly, some midline structures (falx cerebri, interhemispheric fissure, third ventricle) are present, whereas they are absent in holoprosencephaly. The cerebral cortex is absent in hydranencephaly but displaced in holoprosencephaly. The face is usually normal in hydranencephaly, while midline facial dysmorphism is common in holoprosencephaly.

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