• When the neural tube does not close properly
• Early failure = abnormal brain development, Late failure = spinal cord defects
• Produce an elevation of AFP (produced by fetal GI tract and liver, exits through the NT defect then passes through maternal blood)
• Folic Acid in prenatal vitamins prevents NTD

• Absence of the skull and the cerebral hemispheres
• Neural tube fails to close 2-3 weeks
• Diagnoses as early as 12 weeks
• ONE OF THE MOST COMMON CNS ANOMALIES
• Fatal
  
  

• Cranium - Absent
• Cerebrum - absent
• Membrane covers defect (no skin or bone)
• elevated AFP
• "Frog like facies" - bulging eyes, macroglossia (protruding tongue), short neck

• Polyhydramnios
• increased fetal activity
• major portions of cranium are absent 
• Orbits and face are present (frog like facies)

• Skull is absent, brain is present
• elevated AFP
• can be diagnosed at 12 weeks

herniation of intracranial defects caused by bone defect in skull.

located occipital (most common), frontal or parietal

Elevated AFP

Associated with Meckel-Gruber Syndrome (polycystic kidneys, polydactyly), hydrocephalus, agenesis of CC

Encephalocele: herniated contents includes brain tissue and CSF

Cranial Meningocele: herniated contents includes only meninges and CSF

• Abnormality in cercial vertebrae associated with an excessive bend of the cervico thoracic spine and neural tube closure defects.
• Results in gross hyper-extension of fetal head
• may have cervical or lumbar myelomeningocele
• Elevated AFP
• Prognosis: fatal

• short C-spine with missing vertebrae
• retroflexion of the head "stargazing" position
• anencephaly or severe microcephaly usually present
• often large meningocele seen

A defect of the spinal canal that results in herniation of its contents

cause: neural tube does not fuse at 3-5 weeks; lack of fusion of the posterior laminae

folic acid prevents spina bifida

Defect is covered by skin

cord may be in a normal location

spinal cord may be herniated

normal AFP

tuft of hair over site of defect

skin dimpling

difficult to see, incidental finding

abnormal posterior elements

splaying of bony elements

Myeloschisis

Meningocele

Myelomeningocele

bony elements are open and played

skin defect is present

cord is exposed to fluid

herniation that contains only meningeal membranes and CSF protruding through the defect.

10% of spina bifida cases

Can cause elevated AFP and Arnold-Chiari II syndrome

herniation that contains neural tissue plus the meningeal membranes and CSF protruding through defect.

90% of spina bifida cases

can cause elevated AFP and arnold-chiari II syndrome

Type II: defect where the cerebellar vermis, 4th vent., and medulla oblongota are pulled through the foramen magnum into the upper cervial canal

low brainstem displaces the 4th ventricla, obstructing the aqueduct, causing hydrocephalus

US: Lemon sign, Banana sign, non-visualization of CM

Deformed skull cause by shifted anatomy.

Frontal Bones: being pulled inward

Skull has shape of a lemon

strong indicater of neural tube defect

displaced anatomy alters appearance of cerebellum and CM

cerebellum becomes displaced inferiorly and posteriorly and curves like a banana

CM: < 2mm

Strong indicator of neural tube defect