Neural Axis Abnormalities

What is the most common neural tube defect?

Anacephally

Most common neural tube defect, caused by failure of closure of neural tube at cranial end; result is absence of cranial vault

Anacephally

Anencephaly can result in the complete or partial absence of:

- forebrain
- brainstem
- midbrain
- skull base
- facial structures

What levels increase with anencephaly ?

maternal serum alpha-fetoprotein (AFP)

What are some common causes of anacephally

- Meckel-Gruber
- Chromosomal (T-13, T-18)
- Diabetes
- Environmental and dietary factors
- Amniotic band syndrome

Any open defect contains a high____ level

AFP

True or false with anacephally it’s not lethal

False it is lethal

What should you see in the sonographic appreance of anacephally?

• Absence of the brain and cranial vault

• Buldging fetal orbits, giving it a frog like appearence.

Other findings of anacephally include?

• Polyhydramnios,

• Coexisting spina bifida and/or craniorachischisis ,

• Cleft lip and palate Hydronephrosis

• Diaphragmatic hernia

• Cardiac defects

• Omphalocele

• Gastrointestinal defects Talipes

ACRANIA is an ______, also known as _____

Lethal anomaly, execephaly

What occurs in acrania?

Mesenchymal tissue fails to migrate and does not allow bone formation over the cerebral tissue

With acrania there is an absence of ________ and a presence of ____, although abnormal developement of ____

cranial bones and complete, cerebral hempisphere

With Acrania its assciotated with _______ levels

High maternal serum alpha-fetoprotein (AF) levels

With acrania the sonographic appreance consists of?

The presence of brain tissue without the presence of cranial bones

What are some other findings included in acrania

• Spinal defects

• Cleft lip and palate

• Talipes

• Cardiac defects

• Omphalocele

• Amniotic band syndrome

Disorders that may mimic acrania

Hypophosphatasia and osteogenesis imperfecta

True or false identifying addiional findings like the long bone fractures can help distiguish disorders from acrania

True

Neural tube defect in which meninges alone or meninges and brain herniate through defect in calvarium

CEPHALOCELE

What is the most common form of CEPHALOCELE

Encephalocele when herniated contents include brain tissue and CSF

What is the other form of cephalocele

Cranial Meningocele when herniated contents includes only meninges and CS

With cephalocele prongnoisis based on?

size and location

True or false cephalocele has low maternal serum alpha-fetoprotein (AF) levels

False, its high levels

Describe the sonographic appreance of cephalocele

• Extracranial mass: may be fluid filled or contain solid components

• Cranial defect

• Ventriculomegaly

Defect in the occiput involving the foramen magnum (fusion of occiput spine)

iniencephaly (cause is unknown)

Iniencephaly results in a gross

• hyperextension/retroflexion of the fetal head

• The occpital cranium is directed toward the lumbar spine and may have cervical or lumbar myleomenigocele

With Iniencephaly its ______, _____, and contains _____

Rare, lethal, and elevated AFP (if open defect is detected)

Spindia bifdia is