Notes on neural tube defects

NEURAL TUBE DEFECTS

 Result from failure of normal fusion of neural plate to form neural tube during first
28 days following conception
 Anencephaly, encephalocele, spina bifida occulta, meningocele and
myelomeningocele




Anencephaly Encephalocele

Aetiology
Maternal RFs
 Folate deficiency during pregnancy
 Drugs that interfere with folate metabolism
o Methotrexate
o Anticonvulsants; valproate & carbamazepine
o Sulfonamides
 Pregestational diabetes
 Obesity
 Fever during the first trimester
Foetal causes
 Chromosomal abnormalities (trisomy 13, 18)
 Chiari II malformation
Pathophysiology
 Neural plate appears on 17th day of gestation as a thickening of embryonic ectoderm
 On 18th day neural plate folds along midline
 By end of 3rd gest week, neural folds fuse to form neural tube
 Fusion begins at hindbrain
 Anterior and posterior ends close to form SC
 Depending on point of interruption in neural tube formation, NTDs may affect brain
or SC
Spinal cord defects Brain defects
 Spina occulta  Anencephaly
 Meningocele  Encephalocele
 Myelomeningocele
 Myelocele

Types of spina bifida
Spina bifida occulta
 Failure of fusion of vertebral arch
 No herniation