Spina bifida occulta
Spina bifida occulta refers to a vertebral anomaly consisting of the absence of spinous process and varying amounts of the associated lamina. Usually the central nervous system, cauda equina and meninges are not involved. The neurological examination is normal. Most frequently the skin is normal over the vertebral defect however, associated dimples, sinuses, hypertrichosis (increased hair), fatty lump and hemangiomata (swelling consisting of blood vessels) may indicate the presence of occult lesion.

Spina Bifida Aperta
Meningocele: Meningocele becomes evident at birth with observation of a cystic skin covered midline mass over the back. The dorsal half of one or more vertebrae is absent and the sac is composed of CSF, meninges and skin. The reminder of the CNS is not involved and the prognosis for development is excellent. About 10% of the patients with spina bifida will have meningocele.

Myelomeningocele: Myelomeningocele is most severe form of spina bifida. The middle mass in addition to CSF and meninges contains spinal cord and cauda equina. All of these patients will have Arnold Chiari malformations; most of them will develop hydrocephalus. There is sensory motor loss distal to the lesion which produces neurogenic bladder and varying degree of weakness in lower limbs. Orthopedic deformities are commonly present.

Lipomyelomeningocele: Refers to lesions as described above that are associated with a lipoma. This may be extradural and /or intradural and involve the cauda equina and the conus medularis.

Rachischisis: describes the failure of ectodermal and mesodermal closure that results in the brain and spinal cord being exposed to the environment.