Female, 26 years old, with abnormality seen on fetal ultrasound, assess for spina bifida. The frontal bones demonstrate symmetric bilateral concavity. The ventricular atria are top normal in size measuring up to 10 mm in diameter. The third ventricle is within normal limits. It does appear that the corpus callosum is at least partially present. No definite additional supratentorial lesions are seen, though fetal motion does reduce sensitivity for subtle abnormalities. The posterior fossa is small and crowded. The cerebellum appears to partially enwrap the brainstem. A small posterior soft tissue defect is seen in the sacral region which exposes the lower sacral spinal canal. Image quality does not allow for the visualization of neural elements at this level.
Findings are seen compatible with Chiari II malformation. This includes a small, crowded posterior fossa and the presence of a sacral meningocele or myelomeningocele. Supratentorially, the ventricular atria are top normal in size. It does appear that the corpus callosum is at least partially present. No definite additional supratentorial lesions are seen, but fetal motion significantly reduces the sensitivity for subtle findings.