This document discusses early signs of spina bifida that can be detected on ultrasound as early as the first trimester. It identifies two key signs - the "lemon sign" and "banana sign" - that present differently depending on the trimester. The lemon sign represents abnormal frontal bone development and can be seen as a decreased fronto-maxillary facial angle in the first trimester or scalloping of the frontal bones in the second trimester. The banana sign represents cerebellar herniation and can be seen as proximity of the midbrain to the occiput or anteriorly curved cerebellar hemispheres in the first and second trimesters respectively. These signs allow for early diagnosis of spina

1. Dr.Sameer Dikshit MD, DGO,FCPS,FICOG Fetal Medicine Consultant, Mumbai

2. “ The eye only sees what the mind is prepared to comprehend” Henri Bergson, French Philosopher, 1927 Nobel prize in literature

4. The Lancet, Volume 328, Issue 8498, 1986 K.H.Nicolaides, S.G Gabbe, S. Cambell, R Guidetti 70 fetuses with Ultrasound diagnosis of spina bifida between 16-23 weeks Previous ultrasound records were reviewed

5. In 54 fetuses who had pictures taken at BPD plane showed scalloping of the frontal bones ( Lemon Sign )

6. In 12 of the 21 fetuses for which sub occipito bregnatic plane was taken, showed cerebellar hemispheres curved anteriorly with simultaneous obliteration of Cisterna Magna ( Banana Sign )

7. None of these changes were present in 100 normal fetuses

10. Lemon sign 53% Ventriculomegaly 81% Small Cerebellum 96% Effaced Cisterna Magna 93% Small Posterior Fossa 96%

11. Spinal defect present but no CNS signs 0.04% 100% of the above were closed neural tube defects

12. Lemon sign & Banana sign present in 100% of cases diagnosed as open neural tube defect between 16-24 weeks Detected 1-2 weeks before noticing spinal defect Microcephaly in 69%

13. After 24 weeks, Lemon sign noted only in 25% Microcephaly and Banana sign noted in 100%

14. Evolution of Lemon sign and Banana sign

15. Open neural tube defect Leakage of CSF from the spinal defect Hypotension of Subarachnoid space Prolapse of cerebellum into the foramen magnum

16. Obstructive Hydrocephalus Abnormal Calvarial Development that is characteristic of the “Cranial Signs” Small posterior fossa

17. Arnold Chiari Malformation

18. Knowing earlier is always better than later !!!

19. Extrapolation of Arnold Chiari malformation in 1 st Trimester

20. Acorn shaped head Small HC Parallel Cerebral Peduncles

22. The position of parallel peduncles is visible Visualisation of cerebellum is difficult before 14 weeks & may be confused with choroid plexus of the IV ventricle In sagittal view, the fetuses demonstrated a flat occiput In axial view, the frontal bones are not convex but were retracted giving “acorn shape”

23. The contours of the metencephalon in spina bifida are straighter than normal This could be due to downward displacement of the brain

26. Normal Fetus Spina Bifida

27. 1 st Trimester Equivalent of Banana sign

28. Distance between posterior border of Aqueduct of Sylvius and anterior border of Occiput in Axial Plane AOS-to-Occiput Distance

30. In cases with spina bifida, juxtaposition of the midbrain to the occiput was a clue to the diagnosis In all the cases AOS-to-occiput distance was below the established normal range In contrast to subtle changes in the sagittal view, axial imaging of the midbrain reveals striking changes which can be quantified by AOS-to-occiput distance

32. First Trimester equivalent of Lemon sign

33. In fetuses with open spina bifida, at 11-13 weeks , the frontomaxillary facial angle is decreased and this measurement may be useful in early screening for this abnormality

34. Fronto Maxillo Facial Angle Spina Bifida, decreased angle Normal fetus, normal angle

35. This is due to caudal displacement of the fetal brain due to associated Arnold Chiarri malformation resulting in abnormal development of frontal bones This is thought to be the underlying mechanism for producing “lemon sign”.

36. More technological refinement  3D USG

38. Brain Stem Diameter (BSOB) Brain Stem Occipital Bone Diameter

40. The underlying mechanism of Lemon and Banana sign is the same that is being used to diagnose open neural tube defect in 11-14 weeks More things change, more they remain the same…

41. Thank You