This document discusses prenatal diagnosis of myelomeningocele (spina bifida). It describes myelomeningocele as a failure of neural tube closure, leaving an open spinal defect. Prenatal diagnosis methods include maternal serum alpha-fetoprotein screening, ultrasonography to identify characteristic signs of hydrocephalus and Chiari II malformation, magnetic resonance imaging for greater resolution, and amniocentesis to measure amniotic fluid acetylcholinesterase levels to increase diagnostic accuracy of alpha-fetoprotein levels.

1. Prenatal Myelomeningocele
Treatment and Diagnosis
Learn more about
Myelomeningocele and Spina Bifida
at http://www.spinabifida.net

2. Terminology
• Myelomeningocele
- Results from failure of proper neural tube closure
during primary neurulation.
- Leaves a flat plate of neural tissue called the
neural placode.
- As a result, the overlying mesodermal and
ectodermal elements fail to form and an open
spinal defect is produced.
- Associated with a Chiari II malformation.

4. Prenatal diagnosis
• Maternal Serum Alpha Fetoprotein
- Initial screen for NTDs.
- In amniotic fluid, the AFP conc. is 100-fold less than in fetal
CSF.
- Sampling at GA 16-18 wks
- MSAFP level of 1.5 multiples of the median  risk of 1 in
2317 for an open NTD.
- MSAFP level of 2.5 multiples of the median  risk of 1 in
98 for an open NTD.
- Diagnostic accuracy 60-70%
- If risk > 1 in 500  further U/S is recommended
- False positive of MSAFP levels : incorrect estimated GA,
multiple pregnancy, fetal demise

5. Prenatal diagnosis
• Ultrasonography
- The sensitivity is nearly 100% in prenatal
screening for NTDs.
- Visualize two cranial abnormalities :
- characteristic of hydrocephalus  “lemon sign”
scolloping of the frontal bones on a biparietal
view
- Chiari II malformation associated with spina
bifida  “banana sign” abnormally shaped
midbrain, elongated cerebellum, obliteration of
the cisterna magna

7. Prenatal diagnosis
• Magnetic Resonance Imaging
- Prenatal MRI is increasingly being used to
examine fetal neurological anomalies.
- Provides greater resolution than U/S.

8. Prenatal diagnosis
• Amniocentesis
- The amniotic AChE level is used to increased
the diagnostic accuracy of the amniotic AFP
level.
- In NTD : neural AChE from CSF leaks into the
amniotic fluid.
- Accuracy of 99%, false positive of 0.34%

9. Questions?
• For more educational resources please visit
http://www.spinabifida.net

10. Questions?
• For more educational resources please visit
http://www.spinabifida.net