Snapshot A 38-year-old woman at 12 weeks gestation presents to her obstetrician for prenatal care. She denies any vaginal discharge, bleeding, and at times notices fetal movement. She has a medical history of seizures. Laboratory testing is significant for an elevated α-fetoprotein level. On ultrasound, polyhydramnios is appreciated with an absence of the brain and calvaria. It was explained to her that her fetus is diagnosed with anencephaly. Introduction Embryology neurulation at the third week of gestation the process of neural tube formation which gives rise to the login to view 1 more bullet impairment in neurulation results in login to view 1 more bullet process login to view 24 more bullets Etiologies folic acid deficiency syndromes such as Chiari II malformation medications such as valproic acid and other login to view 7 more bullets Neural Tube Defects Neural Tube Defects Neural Tube Defect Comments Anencephaly Cranial neural tube is exposed due to failure of the rostral neuropore to close at day 25 Findings ↑ AFP ultrasonography shows absence of the brain and calvaria polyhydramnios This is not compatible with survival Spina bifida occulta Secondary tofailure of the caudal neuropore to close without herniation Findings normal AFP tuft of hair or skin dimple at site of bony defect Spina bifida with meningocele Secondary to failure of the caudal neuropore to close with protusion of the meninges through the bony defect Findings ↑ AFP associated with spina bifida cystica Spina bifida with meningomyelcele Secondary to failure of the caudal neuropore to close with protusion of the meninges and spinal cord through the bony defect Findings ↑ AFP associated with Chiari II malformation Spina bifida with myeloschisis Secondary to failure of the caudal neuropore to close with the spinal cord able to be seen externally Findings ↑ AFP ↑ AChE