Spina bifida occurs in three forms, each varying in severity.
Spina bifida occulta
This mildest form results in a small separation or gap in one or more of the bones (vertebrae) of the spine. Because the spinal nerves usually aren't involved, most children with this form of spina bifida have no signs or symptoms and experience no neurological problems.
Visible indications of spina bifida occulta can sometimes be seen on the newborn's skin above the spinal defect, including:
- An abnormal tuft of hair
- A collection of fat
- A small dimple or birthmark
Many people who have spina bifida occulta don't even know it, unless the condition is discovered during an X-ray or other imaging test done for unrelated reasons.
In this rare form, the protective membranes around the spinal cord (meninges) push out through the opening in the vertebrae. Because the spinal cord develops normally, these membranes can be removed by surgery with little or no damage to nerve pathways.
Also known as open spina bifida, myelomeningocele is the most severe form — and the form people usually mean when they use the term "spina bifida."
In myelomeningocele, the baby's spinal canal remains open along several vertebrae in the lower or middle back. Because of this opening, both the membranes and the spinal cord protrude at birth, forming a sac on the baby's back.
In some cases, skin covers the sac. Usually, however, tissues and nerves are exposed, making the baby prone to life-threatening infections.
Neurological impairment is common, including:
- Muscle weakness of the legs, sometimes involving paralysis
- Bowel and bladder problems
- Seizures, especially if the child requires a shunt
- Orthopedic problems — such as deformed feet, uneven hips and a curved spine (scoliosis)