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, and the spinal canal is incomplete. This allows the spinal cord and meninges (the membranes covering the spinal cord) to protrude out of the child's back.
Spina bifida includes any congenital defect involving insufficient closure of the spine. Myelomeningocele accounts for about 75% of all cases of spina bifida and may affect as many as 1 out of every 800 infants. The rest of the cases are most commonly spina bifida occulta (where the bones of the spine do not close, the spinal cord and meninges remain in place, and skin usually covers the defect) and meningoceles (where the meninges protrude through the vertebral defect but the spinal cord remains in place).
The cause of myelomeningocele is unknown. However, folic acid deficiency is thought to play a part in neural tube defects. The disorder appears to be more common in families. If a child is born with myelomeningocele, subsequent children in that family have a higher risk than the general population.
A viral cause or trigger has been theorized because there is a higher incidence of the defect in children born in the early winter months. Research also indicates possible environmental factors such as radiation.
Protrusion of the spinal cord and meninges damages the spinal cord and nerve roots, causing a decrease or lack of function of body areas controlled at or below the defect. Symptoms are related to the anatomic level of the defect. Most defects occur in the lower lumbar or sacral areas of the back (the lowest areas of the back) because this area is normally the last part of the spine to close.
Symptoms include partial or complete paralysis of the legs, with partial or complete lack of sensation, and may include loss of bladder or bowel control. The exposed spinal cord is susceptible to infection (meningitis).
Other congenital disorders may also be present in the child, usually disorders of the spinal cord or the musculoskeletal system such as hydrocephalus (which may affect as many as 90% of children with myelomeningocele), syringomyelia, hip dislocation, or similar disorders.
