Lemon and banana sign


This case shows some easily recognizable features on regular axial projections in fetal imaging, to suggest a neural tube defect like Chiari malformation.

A physiological analog of Chiari malformation that could be thought for memorizing is, as if skull is trying to push the brain matter out of its opening (foramen magnum), by pinching from front, and compressing the fossa from behind, and pushing the tonsils or brainstem out of foramen magnum. This gives rise to 'lemon sign' and 'banana sign'.