Myelomeningocele is a sacculation of the meninx and spinal cord through a vertebral defect that develops because of a closure defect of the posterior neuropore
, which is the latest phase of neurulation in the third and fourth weeks of gestation.
Spina bifida in curly tail mice (ct-/ct-) results from a defective closure of the posterior neuropore
, which forms the caudal region of the neural tube.
Spina bifida with rachischisis occurs when the posterior neuropore
of the neural tube fails to close during week 4 of development.
Until complete fusion of the neural plate, the cranial and caudal ends of neural tube communicate with the amniotic cavity through anterior and posterior neuropores
. Closure of cranial neuropore occurs at about 25th day (8-20 somite stage) whereas the posterior neuropore
closes at about 28th day (25 somite stage).