Banana sign seen in the fetal brain suggests

(C) Spina bifida # Spina Bifida:> Spinal dysraphism, spinabifida, is the incomplete closure of the neural tube.> It may be Spina bifida aperta, Spina bifida Cystica, or Spina bifida occulta.> Spina bifida Cystica is associated with > 90% neurological defects --- 1. Simple Meningocele, 2. Myelocele, 3. Myelomeningocele, 4. Myeloschisis.> Myelomeningocele is associated with 1. Hydrocephalus (70-90%), 2. Chiari II malformation (100%), 3. Congenital/acquired kyphoscoliosis (90%) 4. Vertebral anomalies, 5. Diastematomyelia, 6. Duplication of central canal, 7. Hemimyelocele, 8. Hydromyelia & 9. Chromosomal anomalies (trisomy 18, 13, &triploidy).> Ultrasonography of cranium in Spina bifida (myelomeningocele) shows: Banana Sign: Obliteration ofcisterna magna with cerebellum wrapped around posterior brainstem secondary to downward traction of spinal cord in Arnold Chiari malformation type II (in 96% of fetuses > 24 weeks). Lemon Sign: concave/linear frontal contour abnormality located at coronal suture associated with nonskin covered myelomeningocele (in 98% of fetuses < 24 weeks + 13% of fetuses > 24 weeks) Other features include -- nonvisualisation of cerebellum, effaced cysterna magna (100% sensitivity), ventriculomegaly etc.