Banana sign (cerebellum)

Dr Henry Knipe and A.Prof Frank Gaillard et al.

The banana sign is one of the many notable fruit inspired signs.

It is seen on axial imaging through the posterior fossa of the fetus and is associated with the Chiari II malformation. It describes the way the cerebellum is wrapped tightly around the brain stem as a result of spinal cord tethering and downward migration of the posterior fossa contents. The cisterna magna gets obliterated and the shape of the cerebellum has the appearance of a banana. The sign persists into the second and third trimesters.

The banana sign is also seen in the majority of fetuses with spina bifida, but disappears after 24 weeks. There is very frequently concurrent hydrocephalus.

Associated signs

The same condition also gives rise to the lemon sign.

Inspired signs
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Article information

rID: 963
System: Obstetrics
Section: Signs
Tag: stub, cases
Synonyms or Alternate Spellings:
  • Banana cerebellum

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Cases and figures

  • Figure 1: photograph: banana
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  • Case 1
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  • Case 2: lemon and banana sign
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  • Case 3
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