Neural Tube Defects

 

Epidemiology and Etiology:

·         Anencephaly:

o   1-5 / 1000 live births

o   F > M

·         Unknown etiology

·         Folate deficiency is a risk factor

 

Common sites:

·          

 

Gross features:

·         Spina bifida (spinal dysraphism)

o   Asymptomatic bony defect or a severe malformation with a flattened, disorganized segment of spinal cord

·         Myelomeningocele

o   Extension of CNS tissue through a defect in the vertebral column

o   Lumbosacral most common

·         Meningocele

o   Malformation involving only bone, soft tissues, and meninges, no neural tissue

·         Anencephaly

o   Absence of brain and calvarium

·         Posterior fossa structures may be spared

o   Area cerebrovasculosa in its place

·         Encephalocele

o   Diverticulum of malformed CNS tissue through a defect in the cranium

o   Occipital or posterior fossa most common

 

Histologic features:

·         Meningocele:

o   Meningothelial cells

o   Loose fibrovascular connective tissue

o   Peripheral nerve twigs maybe

o   Spinal nerve roots maybe

o   Smooth muscle bundles maybe

o   Dendritic melanocytes maybe

o   Nodules of mature adipose tissue maybe (lipomeningocele)

·         Myelomeningocele:

o   As meningocele but also contains neuroglial tissue

·         anencephaly:

o   area cerebrovasculosa:

·         remnant of disorganized brain tissue with admixed ependyma, chroid plexus, and meningothelial cells

 

Immunophenotype:

Marker:

Sensitivity:

Specificity:

 

 

 

 

Molecular features:

 

Other features:

·         serum elevated alpha-fetoprotein (AFP) in amniotic fluid and mother’s serum

o   AFP is the fetal version of albumin and leaks out of defect into amniotic fluid

·         clinical features:

o   cord dysfunction if cord is disorganized

·         complications:

o   infection through thin overlying skin (or defect)

·         counseling:

o   recurrence risk 4-5% (but depends on underlying population incidence)

 

References: