Neural Tube Defects

What is a neural tube defect (NTD)?

neural tube fails to close or form properly

How do you reduce the risk for neural tube defects?

supplement folate aka folic acid

What are the most common NTDs?

anencephaly and spina bifida

What lab value is elevated with open defects?

AFP

What is acrania?

• absence of cranial vault above the orbits

• can be with or without a brain

What is anencephaly?

• type of acrania where there is no brain and also no cranium

• frog-like bulging eyes

What is exencephaly?

• normal amount of brain tissue, but missing skull

• appears as misshapen head with no hyperechoic bone surrounding head

In which disorders does the neural tube fail to close causing a gap between the vertebrae/splaying of the vertebral laminae?

spina bifida and Arnold-Chiari II malformation

What is spina bifida occulta?

• closed type of spina bifida

• defect covered by skin and no herniation of spinal cord outside the body, defect in vertebrae only

• normal AFP

What is spina bifida aparta?

• open types of spina bifida

• two types—meningocele and myelomeningocele

• not covered by skin and result in herniation of spinal contents

• elevated AFP

What is a meningocele?

• only meninges is herniating out

• sac-like cystic appearance

What is a myelomeningocele?

• most common type of spina bifida aperta

• herniation of both meninges and nerve roots

• most commonly in lumbosacral area

Which area is the most common area for a myelomeningocele?

lumbosacral area

What is spina bifida aperta strongly associated with?

Arnold-Chiari II malformation

What is Arnold-Chiari II malformation?

When the presence of an open spina bifida pulls down on the spinal contents causing cranial malformations

What are the three key findings of Arnold-Chiari II malformation?

• lemon shaped head

• banana cerebellum

• obliterated cisterna magna

What is a cephalocele/encephalocele?

• herniation of intracranial contents through opening in skull

• abnormal AFP

What is the most common location for a cephalocele/encephalocele?

occipital location

What disorder are cephaloceles/encephaloceles associated with?

Meckel-Gruber

What is Meckel-Gruber?

occipital cephalocele and PKD

What is inencephaly?

• hyperextension of neck

• closed NTD—AFP normal

• “star-gazer”