Congenital Abnormalities of Vertebral Column and Spinal Cord
Spina Bifida Occulta
- Results from vertebral arch failing to fuse in midline
- Frequently occurs at L5 or S1 and may be marked by a tuft of hair and/or pigmented skin
- Not associated with any neurological deficit
Spina bifida occulta is usually asymptomatic and detectable only by x-ray.
Spina Bifida Cystica
- Protrusion of meninges and/or spinal cord through defect in vertebral arches
- Occurs in about 1:1000 births
- Often detected through high levels of alpha-fetoprotein in maternal serum or amniotic fluid
Neural tube defects cause high alpha-fetoprotein levels in maternal serum and amniotic fluid.
- May have reduced incidence with vitamin and folic acid supplements before conception and increased incidence with anticonvulsant valproic acid during week 4
Neural tube defects may be preventable by folic acid supplements before and during pregnancy.
- Spinal meningocele
- Protrusion of meninges through a defect in vertebral arches
- May be associated with neurological deficits
Meningomyelocele is congenital protrusion of spinal cord and nerve roots through vertebral defect with neurological damage.
- Protrusion of spinal cord and/or nerve roots in meningeal sac
- Causes neurological deficits that depend on level and extent of lesion
If only nerve roots are involved in spina bifida with meningomyelocele, resultant paralysis is flaccid (lower motor neuron lesion), but spinal cord damage results in spastic paralysis (upper motor neuron lesion); mixed types of paralysis may occur. Hydrocephalus commonly develops due to herniation of the brainstem and cerebellar tonsils through the foramen magnum (Arnold-Chiari malformation). The exposed meninges and spinal cord are vulnerable to infection.