Definition of Myelomeningocele:

Myelomeningocele is a birth defect in which the backbone and spinal canal do not close before birth. The condition is a type of spina bifida.

Causes, incidence, and risk factors:

Myelomeningocele is one of the most common birth defects of the central nervous system. It is a neural tube defect in which the bones of the spine do not completely form, resulting in an incomplete spinal canal. This causes the spinal cord and meninges (the tissues covering the spinal cord) to stick out of the child's back.

Myelomeningocele accounts for about 75% of all cases of spina bifida and may affect as many as 1 out of every 800 infants. Spina bifida includes any birth defect involving insufficient closure of the spine.

The rest of myelomeningocele cases are most commonly:

• Spina bifida occulta, a condition in which the bones of the spine do not close but the spinal cord and meninges remain in place and skin usually covers the defect
• Meningoceles, a condition where the tissue covering the spinal cord sticks out of the spinal defect but the spinal cord remains in place.

Other congenital disorders may also be present in the child. Hydrocephalus may affect as many as 90% of children with myelomeningocele. Other disorders of the spinal cord or musculoskeletal system may be seen, including syringomyelia and hip dislocation.

The cause of myelomeningocele is unknown. However, folic acid deficiency is thought to play a part in neural tube defects. Also, if a child is born with myelomeningocele, subsequent children in that family have a higher risk than the general population.

Some theorize that a virus make play a role, since there is a higher rate of this condition in children born in the early winter months. Research also indicates possible environmental factors such as radiation.