Which ultrasound sign is associated with neural tube defects, describing a crescent-shaped cerebellum?

• A. Banana Sign
• B. Corpus Callosum
• C. Bladder Exstrophy
• D. Frontal Bossing

Answer: (A)

The main concept is recognizing the banana sign, an ultrasound marker for neural tube defects. In fetuses with open neural tube defects (such as myelomeningocele), a Chiari II malformation often develops, pulling the hindbrain structures downward through the foramen magnum and crowding the posterior fossa. This causes the cerebellum to appear curved in a crescent shape on the ultrasound, called the banana sign. It’s a strong clue pointing toward neural tube defects and prompts further evaluation and counseling. The other findings refer to different anatomy or conditions and do not describe this posterior fossa crowding or cerebellar silhouette.