Lemon and Banana signs


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My presentation on Lemon and Banana signs at AICOG 2012 at Varanasi

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Lemon and Banana signs

  1. 1. Dr.Sameer Dikshit MD, DGO,FCPS,FICOG Fetal Medicine Consultant, Mumbai
  2. 2. “ The eye only sees what the mind is prepared to comprehend” <ul><li>Henri Bergson, French Philosopher, 1927 Nobel prize in literature </li></ul>
  3. 4. <ul><li>The Lancet, Volume 328, Issue 8498, 1986 </li></ul><ul><li>K.H.Nicolaides, S.G Gabbe, S. Cambell, R Guidetti </li></ul><ul><li>70 fetuses with Ultrasound diagnosis of spina bifida between 16-23 weeks </li></ul><ul><li>Previous ultrasound records were reviewed </li></ul>
  4. 5. <ul><li>In 54 fetuses who had pictures taken at BPD plane showed scalloping of the frontal bones ( Lemon Sign ) </li></ul>
  5. 6. <ul><li>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 ) </li></ul>
  6. 7. <ul><li>None of these changes were present in 100 normal fetuses </li></ul>
  7. 10. <ul><li>Lemon sign 53% </li></ul><ul><li>Ventriculomegaly 81% </li></ul><ul><ul><ul><ul><li>Small Cerebellum 96% </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Effaced Cisterna Magna 93% </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Small Posterior Fossa 96% </li></ul></ul></ul></ul>
  8. 11. <ul><li>Spinal defect present but no CNS signs 0.04% </li></ul><ul><li>100% of the above were closed neural tube defects </li></ul>
  9. 12. <ul><li>Lemon sign & Banana sign present in 100% of cases diagnosed as open neural tube defect between 16-24 weeks </li></ul><ul><li>Detected 1-2 weeks before noticing spinal defect </li></ul><ul><li>Microcephaly in 69% </li></ul>
  10. 13. <ul><li>After 24 weeks, Lemon sign noted only in 25% </li></ul><ul><li>Microcephaly and Banana sign noted in 100% </li></ul>
  11. 14. Evolution of Lemon sign and Banana sign
  12. 15. <ul><li>Open neural tube defect </li></ul><ul><li>Leakage of CSF from the spinal defect </li></ul><ul><li>Hypotension of Subarachnoid space </li></ul><ul><li>Prolapse of cerebellum into the foramen magnum </li></ul>
  13. 16. <ul><li>Obstructive Hydrocephalus </li></ul><ul><li>Abnormal Calvarial Development that is characteristic of the “Cranial Signs” </li></ul><ul><li>Small posterior fossa </li></ul>
  14. 17. Arnold Chiari Malformation
  15. 18. Knowing earlier is always better than later !!!
  16. 19. Extrapolation of Arnold Chiari malformation in 1 st Trimester
  17. 20. <ul><li>Acorn shaped head </li></ul><ul><li>Small HC </li></ul><ul><li>Parallel Cerebral Peduncles </li></ul>
  18. 22. <ul><li>The position of parallel peduncles is visible </li></ul><ul><li>Visualisation of cerebellum is difficult before 14 weeks & may be confused with choroid plexus of the IV ventricle </li></ul><ul><li>In sagittal view, the fetuses demonstrated a flat occiput </li></ul><ul><li>In axial view, the frontal bones are not convex but were retracted giving “acorn shape” </li></ul>
  19. 23. <ul><li>The contours of the metencephalon in spina bifida are straighter than normal </li></ul><ul><li>This could be due to downward displacement of the brain </li></ul>
  20. 26. <ul><li>Normal Fetus </li></ul><ul><li>Spina Bifida </li></ul>
  21. 27. 1 st Trimester Equivalent of Banana sign
  22. 28. <ul><li>Distance between posterior border of Aqueduct of Sylvius and anterior border of Occiput in Axial Plane </li></ul><ul><li>AOS-to-Occiput Distance </li></ul>
  23. 30. <ul><li>In cases with spina bifida, juxtaposition of the midbrain to the occiput was a clue to the diagnosis </li></ul><ul><li>In all the cases AOS-to-occiput distance was below the established normal range </li></ul><ul><li>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 </li></ul>
  24. 32. First Trimester equivalent of Lemon sign
  25. 33. <ul><li>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 </li></ul>
  26. 34. Fronto Maxillo Facial Angle <ul><li>Spina Bifida, decreased angle </li></ul><ul><li>Normal fetus, normal angle </li></ul>
  27. 35. <ul><li>This is due to caudal displacement of the fetal brain due to associated Arnold Chiarri malformation resulting in abnormal development of frontal bones </li></ul><ul><li>This is thought to be the underlying mechanism for producing “lemon sign”. </li></ul>
  28. 36. More technological refinement  3D USG
  29. 38. <ul><li>Brain Stem Diameter </li></ul><ul><li>(BSOB) Brain Stem Occipital Bone Diameter </li></ul>
  30. 40. <ul><li>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 </li></ul>More things change, more they remain the same…
  31. 41. Thank You