Various subtypes exist:

• Spina bifida occulta:
  • incidence is 1 : 500
  • one or more vertebral arches failed to close, spinal cord and meninges are normal
  • intact skin over the defect may be hairy and hyperpigmented
  • does not cause symptoms, spina bifida occulta is usually diagnosed accidentally
• Spina bifida cystica:
  • incidence is 1 : 1000.
  • there is a cyst protruding through the defect in the vertebral arches
  • according to the contents of the cystic protrusion these variants can be recognized:
    • Meningocele: cystic sac contains dura mater, arachnoid and cerebrospinal fluid. Neither the spinal cord nor the spinal nerves are malformed.This occurs in 15% of cases.
    • Meningomyelocele: the cystic sac also contains the spinal cord and the spinal nerves (in addition to the meninges), which adhere to the sides of the sack. This occurs in 85% of cases. Hzdrocephalus (Arnold Chiari malformation) is invariably associted. Symptomatology corresponds with localisation of the defect, for example if the defect is in the sacral area, there is loss of bladder and bowel function. The sac can become infected and there is a risk of ascendent meningitis. Surgery is necessary right after the birth.