November 18, 1999
Spina bifida is a relatively common birth defect
which occurs in 1 to 2 of every 1,000 babies born in the United States.
"Spina bifida" literally means "split spine"; it is
caused by failure of the spinal cord to develop properly.
The nervous system develops from embryonic tissue called the ectoderm.
The first sign of the developing nervous system is the neural plate which
can be seen at about the 16th day of development. Over the next few days,
a "trench" is formed in the neural plate - this creates a neural
groove. By the 21st day of development, a neural tube is formed when the
edges of the neural groove meet. 
The rostral (front) part of the neural tubes goes on to develop into the
brain and the rest of the neural tube develops into the spinal cord. Spina
bifida occurs when the neural tube is not formed properly; the bones of
spinal column (the vertebrae) and muscle fail surround the spinal cord
properly. No one knows exactly what causes spina bifida, but it is thought
that both environmental and genetic factors
play a role.
Skull andVertebrae
Development of the Nervous System
Failure
of the neural tube to develop properly may result in three different conditions
that lead to spina bifida:
Two recent papers in the Journal
of the American Medical Association describe the results of attempts
to fix the defect in the spinal cord while babies are still developing
within their mothers. During this procedure, surgeons open the womb of
the mother and repair the damaged back of the baby. Doctors at Children's
Hospital in Philadelphia and at Vanderbilt University Medical Center report
that the need for shunts was decreased and the incidence of hindbrain
swelling was reduced after this procedure.