What is Myelomeningocele or Spina Bifida?
Myelomeningocele, more commonly known as Spina Bifida, is an open spinal cord defect, usually located in the lower back. In this defect there is an opening in the vertebral body or the bone that surrounds the spinal cord in the lower spine. This can be located anywhere from the upper back to the very bottom of the spine. The cause of myelomeningocele is unclear, but it is felt to be due to a failure of the neural tube to close during early fetal development. This abnormal closure occurs approximately 2-3 weeks following conception. The result is a defect in the bones around the spinal cord, a defect in the tissues covering the spinal cord called the meninges, and a defect in the spinal cord. The spinal cord and surrounding tissues protrude through the opening in the spine and are not covered by skin. These tissues are then exposed to the amniotic fluid during pregnancy, and this exposure and potential risk of trauma to these areas during in utero development can result in further nerve injury. The most common complications from spina bifida are a disruption in the nerves at and below the affected area. These defects can result in abnormal sensation and loss of muscle control or movement from the level of the defect and lower. This can include problems with movement in the legs and the hips, problems with control of the bladder or bowel function, and problems with sensation from the level of the lower chest to the feet. The degree of these impairments is related to where on the spine the lesion is located, referred to as the spinal ‘level’ of the lesion. The location of the lesion is based on the level of the upper most vertebra that is abnormally formed. A second complication from open Spina Bifida results from decreased in pressure in the brain or intracranial pressure. This results in a downward movement of the lower portion of the brain, the cerebellum, towards the back and spine, into the spinal column. As a result of this herniation, a blockage in flow of the normal cerebrospinal fluid in the brain can occur, leading to excess fluid building up in the brain, called hydrocephalus. Hydrocephalus can result in further developmental problems in the brain.
Myelomeningocele is fortunately rare but remains one of the more common birth defects. Myelomeningocele occurs in the United States in 0.5-1 per 1,000 births. Neural tube defects can be part of a chromosome abnormality, a genetic syndrome, or as an isolated birth defect. When isolated, myelomeningocele are thought to be multifactorial in origin, meaning both environmental and genetic factors play a role in their development. Various risk factors have been identified that may increase the risk for neural tube defects. These can include diabetes in the mother or a mother’s use of certain medications including diuretics and seizure medications. Low dietary folic acid intake has also been implicated in an increased risk for Spina Bifida. In addition, mothers with certain defects in folic acid metabolism carry an increased risk for Spina Bifida. Folic acid supplementation is known to decrease the incidence of neural tube defects; however, it is not sufficient to eliminate the condition. Most children with spina bifida are born to women with no risk factors.
How is spina bifida diagnosed?
What testing is recommended for the fetus (baby) when spina bifida is suspected? There are two main methods for evaluating for spina bifida during pregnancy, maternal blood testing and ultrasound. In the first case, elevated levels of alpha fetal protein found in mother’s blood can suggest an increased risk for spina bifida. This blood test is usually performed during the 2nd trimester of pregnancy (15-20 weeks gestational age) in conjunction with Down syndrome screening. In cases of open neural tube defects, such as spina bifida, AFP is noted to be elevated 2 to 7 times over the unaffected population. MSAFP is elevated in 80% of cases of open spina bifida.
When an elevated MSAFP is found on maternal blood screening, a detailed, or ‘targeted,’ ultrasound is then performed to evaluate for an open neural tube defect. Ultrasound is very sensitive and accurate for the detection of myelomeningocele and open Spina Bifida. In most cases, the open spinal defect with associated fetal head abnormalities is identified on ultrasound. The ultrasound evaluation of the baby with spina bifida will identify abnormally shaped and open vertebrae in the affected portion of the fetal spine. A sac containing the dura or menenges, the covering of the spinal cord, can often be identified on the ultrasound. Another finding that can be seen with spina bifida is abnormal positioning of the feet called “clubbed feet”. Fetal head abnormalities are also common findings in spina bifida. Such findings may include ventriculomegally, or enlargements in the fluid containing portions of the fetal brain, abnormal size and shape of the fetal head with narrowing of the bones in the front portion of the fetal skull called the ‘Lemon Sign,’ or an abnormal shaped cerebellum called the ‘banana sign.’ This abnormality of the cerebellum, termed the ‘Chiari Malformation’ results from downward displacement of the cerebellum into the upper portion of the spinal canal.
When open spina bifida is suspected, a very detailed or targeted ultrasound by high-risk pregnancy physicians, such as Maternal Fetal Medicine physicians, in centers that care for high-risk pregnancies is recommended. This ultrasound is performed to evaluate the presence of other fetal abnormalities and assess the spinal level of the lesion. A detailed ultrasound is important to exclude other fetal abnormalities that can alter the overall prognosis. Between 2-15% of cases of open spina bifida also have karyotype or single-gene disorders that may detectable at time of amniocentesis or with further testing. The risk of a chromosome abnormality is increased when additional fetal abnormalities are identified. The presence of chromosome abnormalities also highly alters the prognosis, thus amniocentesis is typically recommended in most cases of spina bifida. In certain cases, a fetal MRI may be performed which can further clarify the overall spinal level of the lesion as well as identify subtle brain abnormalities. Once a diagnosis is suspected, a consultation is performed with Maternal Fetal Medicine and Genetic Counselors to review the diagnosis and discuss the findings on ultrasound.
Management of pregnancy with Spina Bifida
At UNC, management of babies with suspected spina bifida is undertaken by a multidisciplinary team of specialists with extensive experience in the care of pregnancies and children affected by spina bifida. The team approach is coordinated by the UNC Center for Maternal and Infant Health in which all parents are matched with a care coordinator to help guide and plan care through the course of the pregnancy and childhood. This multidisciplinary team includes specialists in Maternal Fetal Medicine (‘High-risk Obstetrics), Genetic Counseling, Pediatric Neurosurgery, Physical Medicine and Rehabilitation, Social Workers, and Neonatologists. Prenatal consultation with each of these specialists will be done to discuss the overall prognosis, care during the pregnancy, and care in the neonatal period, as well as to establish long-term care for the baby. During pregnancy, serial ultrasounds approximately every 4-6 weeks will be performed to evaluate the overall growth of the baby and assess for the development of hydrocephalus.
There is no cure for spina bifida. In some cases, as outlined here [link to fetal surgery section], the baby may be a candidate for in utero repair of the meningomyelocele which may improve the long term outcome in selected cases. This procedure is available at UNC and your care team will evaluate you and your baby to determine if this is the best option for you.
It is recommended that all babies with spina bifida be delivered at a hospital that can provide immediate specialty evaluation and care, including neurosurgical care, for the baby. At this time, most babies with spina bifida are delivered at term, either by cesarean delivery or vaginally, after the natural onset of labor. The route of delivery, whether vaginal or by cesarean, remains controversial and may be individualized based on the specific baby and mother. As older literature suggests a difference in 1-2 levels of function between vaginal delivery and cesarean (slightly worse function after vaginal delivery compared to cesarean), some institutions recommend delivery by cesarean for all patients with spina bifida. However, this data likely does not account for improved neonatal surgical techniques, and may not improve the outcome for the baby in all cases and delivery is individualized. Thus, in most cases of otherwise normal fetal development, normal head size and head first presentation with typical lesions many offer vaginal delivery.
Given the significant long-term risks of complications, need for surgical intervention and risk of poor neurodevelopmental outcome when the diagnosis is made < 20 weeks gestational age, the option of not continuing the pregnancy is discussed with the family.
At the time of delivery, either by cesarean or by a vaginal delivery, neonatal critical care staff including neonatologists will be present in the delivery room. Immediately upon delivery, the baby will be examined, and the defect in the spine is covered with sterile dressing. After visiting with the parents, the baby is then taken to the Newborn Critical Care Center. In most instances, surgical repair of the spina bifida is undertaken within 72 hours. In the first few days of life, serial ultrasounds and a MRI of the fetal head will be performed, and these may need to be repeated to evaluate for the development of hydrocephalus. In the majority of cases, sometimes only after initial repair, hydrocephalus develops and requires placement of a ventriculo-peritoneal shunt. A ventriculo-peritoneal shunt is an implanted catheter that is placed between the fluid-filled areas in the brain, the lateral ventricles, and tunneled under the skin into the abdominal cavity to drain the excess cerebrospinal fluid. This shunt allows for optimal brain development.
We will help encourage and assist mom with nursing the baby as he or she recovers from the surgery and the pediatricians will help mom learn how to care for the baby after the surgery. Following stabilization and recovery from their repair, the baby is able to go home with parents. Follow up care with Physical Medicine and Rehabilitation and Pediatric Neurosurgery Clinics as well as Neonatal Developmental Clinic will be arranged for long-term care for the baby.
Long-term complications and outcomes
Overall, with modern care, many children with spina bifida can lead healthy lives. As many as 90% of children with spina bifida can survive to adulthood with 80% of those with normal intelligence and many leading active lives including participate in sports. www.spinabifidaassociation.org.
While pregnancy, newborn, and long term care of children with spina bifida continues to improve, there can remain long-term complications following the diagnosis of spina bifida and after post-natal repair. While the techniques of neonatal repair and management of developmental complications and long-term complications are improving, there remains a high risk of mortality in the first few years after diagnosis. Unfortunately, approximately 14-35% of children born with spina bifida do not survive by 5 years of age. The overall mortality is highly related to the level of the lesion with lesions lower than the third lumbar level having better long-term outcomes. Evaluation of long-term outcomes based on sensory level in the newborn period has been evaluated. Sensory levels below L3, the third lumbar level, carry a better prognosis with 75% survival to adulthood, 80% of who will have normal IQ, and 90% will be able to walk either unassisted or with orthotics. However, lesions above this level from the T11-L3 region have a more guarded prognosis, with 55% survival to adulthood, 40% who are able to walk assisted or unassisted, and 70% with a normal IQ. Overall, approximately 15% of survivors after the newborn or early childhood repair require some degree of long-term care assistance with normal day to day activities.
The major complications associated with spina bifida include motor and sensory function. The level of the lesion directly impacts the level of injury to the nerves. In general, the ‘upper level’ of the lesion at the time of delivery indicates a level below which nerve function is impaired. This can result in abnormalities in sensation and ability to move muscles below that level. Most of these abnormalities result in problems in the pelvis and lower legs. To be able to stand, a function at the L3 level, or third lumbar, is necessary. Ability to walk requires function at the L4-L5 level, and sexual function in males requires function in the S2-S4. Prenatal ultrasound and prenatal MRI have been shown to correlate with the postnatal level of lesion within one or so levels. So, prediction of motor function, while not precise, can often be estimated in the prenatal period. Your physician will review the suspected level of the lesion of your baby during the prenatal as well as newborn period to estimate the expected impact on your baby.
Many patients with spina bifida also have long-term cognitive impairments with approximately 50% of all cases of spina bifida have some degree of learning disability. One-quarter of patients will have IQ >100, which is in the normal range while one-quarter will have IQ <50, which is consistent with severe impairment. Close monitoring of developmental milestones through spina bifida and neurodevelopmental clinics in the newborn and early childhood timeframes can identify these abnormalities and allow early interventions. Recognition of these risks allows early developmental interventions and promotes optimal development.
As most of these lesions will be above the level of the sacral nerves a common complication is difficulty with control of bladder and bowel function. There is a high risk of bladder and bowel dysfunction that often times results in either incontinence or problems with constipation and difficulty voiding. These often times require early onset clean catheterization or placement, of a tube into the bladder, to drain the bladder. Education on these issues is begun very early in the newborn period. Urologic dysfunction can result in high risk of infection that can ultimately result in renal injury or renal impairment, so careful education of bladder care is an important part of the early management of babies with spina bifida.
Finally a long-term complication of spina bifida that may not become apparent until after surgery is the result of the displacement of the cerebellum, or Arnold-Chiari I malformation. During development this malformation can result in the development of hydrocephalus, or an increased amount of the cerebrospinal fluid that surrounds the brain. An increase in pressure in the brain or an increase in amount of this fluid can result in injury to the surrounding brain tissue. Approximately 80% of cases of spina bifida will develop hydrocephalus. Management of hydrocephalus is required to prevent further brain injury and is usually performed by a surgical procedure in which a tube, or shunt, is placed between the ventricle and the abdomen. This ventriculoperitoneal shunt then bypasses the obstruction to the outflow of the cerebrospinal fluid and can help to prevent brain injury. Shunts carry a small risk for malfunction or infection and often times require revision. In cases of thoracic spina bifida, almost 100% require placement of ventriculo peritoneal shunt, often within the first few days after birth, whereas approximately 80% of lumbar lesions require a ventriculo peritoneal shunt.
Open fetal surgery for repair of myelomeningocele
Given the high risk of long-term complications including motor and sensory dysfunction, hydrocephalus, and risk of learning and developmental disabilities, new techniques for prevention of these complications in cases of spina bifida have been evaluated. The natural history of spina bifida is felt to progress through an initial defect in the spinal cord very early in neonatal development followed by continued injury and poor development of the nerves during the pregnancy and intrauterine life. Thus, the idea of repair of the lesion while the fetus is developing in the womb to prevent these complications has been proposed. In the late 1990’s, in utero repair or open fetal surgery of spina bifida was initiated with the goal to reduce the effects of the defect on the brain and reduce nerve injury at the level of the spinal cord lesion. Pioneering experience was performed at Vanderbilt University, Children’s Hospital of Philadelphia, the University of North Carolina at Chapel Hill, and University of California in San Francisco. In the early 2000’s, sponsored by the National Institute of Health, the MOMs Trial was undertaken where three institutions performed a standardized, controlled trial of in utero repair for spina bifida. The results of this trial were made available in 2011. In this study, in utero repair was performed between the 18th and 25th week of gestation. The pregnant woman underwent general anesthesia, the uterus was opened, and the spina bifida defect was identified and closed. The baby was left in the uterus, the uterine incision closed, and her pregnancy monitored carefully, and the baby was delivered ideally at term. The main goal of this study was to demonstrate a difference in death and placement of ventriculo peritoneal shunt. The MOMS Trial was thought to be highly successful in reducing these complications of spina bifida among those who underwent in utero repair. The rate of shunt placement within 12 months of delivery was decreased from 82% among those who did not have in utero surgery to 40% among those who had uterine surgery. Newborn children at 12 months of age who were noted to have no herniation of the cerebellum or posterior portion of the brain was improved from 4% to 36%. At 30 months of life, in utero repair was also associated with significantly better developmental outcomes and better quality of life as described by the parents. Finally, the proportion of those with a functional lesion level greater than two levels above what was predicted at the time of prenatal diagnosis (better than predicted function) was increased in those with in utero repair from 12% to 32%, and the number of children walking without orthotics at 30 months of life was increased by in utero repair from 21% to 42%.
In utero, or fetal surgery can carry risks both to the baby as well as to the mother. There is a very high rate of preterm birth with the average gestational age of cases undergoing in utero repair delivering at 34 weeks compared to 37 weeks gestational age, and there is a significantly higher rate of pre-term premature ruptured membranes, from 8% to 46%, among the prenatal surgery group. In utero surgery results in an incision in the uterus that requires cesarean delivery for the affected pregnancy as well as all future pregnancies. Finally, given that the pregnancies that underwent in utero repair were delivered at an earlier gestational age with approximately 43% delivered at less than 34 weeks gestational age there was an association of lower birth weight with in utero repair. Finally, a risk of preterm labor and complications of preterm rupture of the amniotic membranes also can result in the need for prolonged hospitalization or prolonged bed rest and reduction in activity of the moms during pregnancy. Currently there is no published data regarding future pregnancy outcomes in women who have undergone fetal surgery for spina bifida.
Despite the increased risk in complications, such as preterm ruptured membranes and preterm birth, overall outcomes including ambulation, motor function, and cognitive and developmental outcomes appeared to be improved in babies with spina bifida following in utero open fetal surgery compared to post-delivery surgery.
The Center for Maternal Infant Health at UNC Chapel Hill including the departments of Maternal Fetal Medicine, Pediatric Surgery, and Pediatrics are proud to offer open fetal surgery for myelomeningocele repair. During the evaluation following the diagnosis spina bifida evaluation for the option for open fetal surgery will be reviewed.
Are we eligible for open fetal surgery for spina bifida?
Each pregnancy diagnosed with spina bifida will be evaluated for the potential for in utero fetal repair. Evaluation required for consideration for open fetal surgery includes a detailed or targeted Maternal Fetal Medicine ultrasound including fetal echocardiogram and fetal MRI to assess the level of the lesion and exclude other complicating diagnoses. An amniocentesis is required for karyotype assessment of the fetus. Finally, evaluation of cervical length as a measure of risk for preterm birth will also be performed. Complete family and genetic history, maternal physical exam, and assessment of obstetrical history will also be performed by Maternal Fetal Medicine and Genetic Counseling. A strong support system for the mom during pregnancy and after delivery is very important to help work through the potential complications of the procedure, potential need for bedrest, and potential need for prolonged hospital care for the pregnancy. Candidates for open fetal surgery include those with a singleton pregnancy, isolated myelomeningocele with upper border below T1 to the level of S1, the presence of an Arnold-Chiari malformation or herniation of the cerebellum, normal karyotype and gestational age between 19-26 weeks at the time of surgery. Patients are excluded from fetal surgery if a secondary major fetal anomaly is noted or if the fetal spine is malpositioned significantly. A high-risk of preterm birth in the mother or prior uterine incision in the active portion of the uterus will also exclude her from safely undergoing fetal surgery. Multiple medical conditions in the mother that can be associated with independent risks of preterm birth may also be exclusions for surgery.
Following the initial maternal and fetal evaluation, care coordination with the Center for Maternal and Infant Health will be performed. Consultation with Pediatric Surgery and Pediatric Neurosurgery, Obstetric Anesthesia, and Neonatal Critical Care Center will be performed. Discussion to explore psychosocial issues regarding plan of care, community support, extensive discussion of open neural tube defects, ability to undergo prolonged hospitalization, and presence of support people will also be discussed with eligible families. As a team, and after discussion with the family, a decision will be made as to whether in utero or after delivery surgery is the best course of treatment for the individual pregnancy.
Potential risks associated with open fetal surgery
Approximately half of patients who undergo fetal surgery will experience preterm, premature rupture of membranes and preterm labor. The development of these complications can often require in-hospital prolonged admission with reduction in maternal activity, time out of work, and time away from family. Preterm birth can result in long term health issues to babies, beyond those due to spina bifida. Prolonged bedrest due to preterm labor or preterm rupture of membranes can increase the risk of infection or blood clots in the mother as well. Finally, open fetal surgery will result in the need for delivery by cesarean section for this pregnancy and for all future pregnancies due to the location of the incision in the uterus.
What happens during open fetal surgery?
In patients who are candidates and elect to undergo open fetal surgery for spina bifida, the procedure is performed as an in-patient procedure. Mom is admitted to labor and delivery the day of, or the evening prior to the procedure. She will receive medications to help prevent preterm labor and antibiotics to prevent infection. The procedure is performed with general anesthesia and a cesarean-type incision is made in the lower abdomen. An incision in the uterus is made at the level corresponding to the location of the lesion on the fetal spine. During this procedure, anesthesia to mom is used to keep the uterus relaxed as well as to provide anesthesia and prevent pain to the baby. The uterus is then opened using special techniques to prevent bleeding, and the spina bifida lesion is exposed. The baby remains in uterus the entire time and is given anesthesia and pain medications. The pediatric neurosurgeon will open the area surrounding the defect, cover the defect in the spinal cord with the dura, then create skin flaps to cover the skin defect. The procedure may require 1-2 hours of anesthesia for the mom.
Following the procedure, the mom will be admitted to Labor and Delivery at which time she’ll receive medication to prevent preterm contractions and preterm labor, including magnesium and Indocin. These medications are continued for 1-3 days depending on presence of uterine contractions. The typical in-patient stay would be approximately 4 days at which time she, if there are no complications, will be able to be discharged home.
Close follow-up following in utero surgery is recommended to continue to follow the status of the mom and baby. At this time weekly to every two week assessment with ultrasound of the baby’s condition, the amniotic fluid surrounding the baby, and evaluation for the development of hydrocephalus is performed. The option for housing such as Ronald McDonald House in Chapel Hill is available for moms who choose to stay in Chapel Hill during the course of their care and management. If complications such as preterm labor or preterm ruptured membranes occur or the fetal status changes such as development of low amniotic fluid, prolonged in-patient evaluation may be necessary. If preterm labor and delivery has not occurred prior to 37 weeks then a cesarean delivery is performed for delivery at 37 weeks estimated gestational age. Delivery is recommended at UNC following this procedure, but delivery at a center with specialty care for spina bifida is also possible.
After delivery, the same close long term developmental follow up as those children undergoing post natal surgery is undertaken
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