Which ultrasound sign is associated with spina bifida?

• A. Lemon sign
• B. Banana sign
• C. Clover sign
• D. Heart sign

Answer: (A)

The main idea is recognizing how spina bifida shows up on fetal ultrasound. The lemon sign is the classic skull contour change seen on an axial view of the fetal head: the frontal bones appear scalloped inward, giving a lemon-like shape. This happens because open spinal defects with associated hindbrain herniation (Chiari II) alter intracranial pressure and brain/ skull growth, producing that characteristic skull shape. It’s a strong, early marker for spina bifida.

Another sign you might hear about is the banana sign, which refers to downward displacement of the cerebellum into the foramen magnum due to the same hindbrain crowding. It often accompanies the lemon sign but the lemon sign specifically describes the cranial contour change that’s most directly linked to spina bifida on ultrasound. The remaining options describe signs not typically used to indicate spina bifida, so they don’t serve as the primary ultrasound marker.