Fetal Surgery: Treating Spina Bifida Before Birth
The spinal cord is a tube-like structure made of nerves and nerve tissue that extends from the brain to the tailbone. It's surrounded and protected by a bony canal called the spine. In normal development, the spine closes completely around the spinal cord. Spina bifida occurs when part of the spine-usually lower in the back-fails to close and leaves the spinal nerves exposed, which can result in mild defects or serious neurological problems.
Spina bifida ranges in severity, commonly taking the following forms:
How common is it?
Spina bifida occurs once in every 1,000 births, with varying severity. MMC is the most common form.
How is it diagnosed?
The brain and spinal cord are surrounded by cerebrospinal fluid (CSF). In spina bifida, CSF leaks into the amniotic fluid through the opening in the spine. This increases the concentration of fetal proteins in the amniotic fluid, especially alpha-fetoprotein (AFP). High levels of AFP can be detected through amniocentesis, a common procedure in which a fine needle is inserted through the mother's abdominal wall and uterus to extract a small amount of amniotic fluid.
AFP eventually enters the mother's blood, where it can also be detected. Elevated levels of the protein (known as maternal serum alpha-fetoprotein) can suggest the presence of spina bifida, but can also indicate other fetal conditions.
Fetal neuroimaging is often necessary to confirm a diagnosis of spina bifida. This includes routine ultrasound and magnetic resonance imaging (MRI), which is painless and free of radiation, and so does not affect the developing fetus.
What can happen before birth?
Recent research shows that prolonged exposure of the spinal cord and nerves to direct trauma and amniotic fluid may be toxic and increase damage to the spinal cord.
Additionally, babies with severe forms of spina bifida often suffer from hydrocephalus, in which an excess of CSF causes the brain to swell. Typically, this fluid must be drained at birth through the placement of a fine tube (shunt).
If there is too much CSF, the brainstem and cerebellum (the parts of the brain that control motor and sensory function) may shift or sag, known as a "Chiari-II" malformation. This can have fatal or near-fatal consequences for the fetus or newborn, including paralysis.
Deformity of the skull in spina bifida: lemon-shaped, instead of smooth oval.
What can be done before birth?
Fetal surgery to treat spina bifida was not available until recently and our program is the first in the region to offer it. In 2011, a study published in the New England Journal of Medicine showed that in most cases, fetal surgery was able to stop CSF from leaking and correct the Chiari-II malformation.* The percentage of affected toddlers walking without assistance at age two and a half was 42 percent when treated with fetal surgery, compared with 21 percent for those treated after birth. The study also showed that fetal surgery reduces the chances of requiring a shunt to correct hydrocephalus.
While the mother is under general anesthesia, an incision is made through the abdominal wall and uterus, exposing the fetus and revealing the spina bifida. The opening in the spine is closed using microsurgical techniques and the fetus is returned to the uterus for the remainder of the pregnancy.
Not all patients qualify for, or would benefit from, this treatment. The operation must be performed early enough in pregnancy (typically before 24 weeks) to be truly effective. The most common complication for the fetus is prematurity: any major surgical intervention on the uterus and the fetus increases the risk of rupturing the membranes and thereby early delivery, sometimes very prematurely. Premature infants are known to be at a greater risk of respiratory, neurological and other complications. Before fetal surgery is recommended, detailed evaluation of the condition and multiple consultations are needed.
What are my delivery options?
If fetal surgery has been performed, the uterus is more fragile and Cesarean section is necessary. A newborn with spina bifida is at risk for severe infections and other complications, so it's recommended that mothers deliver in a center with immediate access to a specialized neonatal intensive care unit and immediate availability of pediatric neurosurgeons and pediatric plastic surgeons.
What will happen at birth?
After the baby with spina bifida is born, he/she will be monitored very closely for any neurological, respiratory or infectious problems. The exposed spinal cord will be protected with a sterile bandage to avoid further injury. Tests will be performed to determine which nerves are affected by the spina bifida.
A consultation with a pediatric neurosurgeon and pediatric plastic surgeon (as well as other specialists, such as urologists) will be obtained rapidly and a procedure to repair the defect typically occurs in the first few days of life. If there is associated hydrocephalus, a shunt to drain the brain of excess CSF may be placed as well.
What is the long-term outcome?
The long-term outcome for babies with spina bifida varies based on the location of the defect (the higher on the spine, the worse the chances of normal lower extremity function) and the presence of other complications.
Hydrocephalus is the most common associated condition; however, as long as the excess fluid in the brain is successfully drained, children can develop normally. Sometimes, the shunts malfunction or become infected, which requires further treatment and operations.
Spina bifida is not usually deadly (although there is an increased of sudden death within the first two years). Neurological and motor function (particularly of the legs) can be affected to varying degrees. Children and adults with spina bifida are at a higher risk of serious infections, including urinary and kidney infections.
*The Management of Myelomeningocele Study, sponsored by the National Institutes of Health.
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