Lemon and Banana signs

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

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

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  • 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
  • 3.  
  • 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
  • 8.  
  • 9.  
  • 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
  • 21.  
  • 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
  • 24.  
  • 25.  
  • 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
  • 29.  
  • 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
  • 31.  
  • 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
  • 37.  
  • 38.
    • Brain Stem Diameter
    • (BSOB) Brain Stem Occipital Bone Diameter
  • 39.  
  • 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