Spine | Spina Bifida
- Myelomeningocele, or an open neural tube defect (NTD), is the most severe form of spina bifida, and occurs when an opening in the spine allows the spinal cord to be exposed.
- This is caused by a failure of the spinal column to close early during fetal development.
- Spina bifida is most often found during the routine anatomical ultrasound at 18-22 weeks gestation.
- Myelomeningoceles are surgically treated after the baby is born but in some cases, surgeons may be able to repair this while the baby is still in the mother’s womb.
Myelomeningocele is a form of spina bifida, which affects approximately 120-150 babies in Canada each year. It is a result of the spinal column failing to close early during fetal development, causing permanent damage to the baby’s spinal cord and nervous system. The spinal cord and the nerves that surround are exposed through the open vertebrae of the spine.
Babies with myelomeningocele may have varying degrees of disability affecting their lower limbs and their bladder or bowel function. The degree of disability depends largely on the location of the spinal defect (with more disability seen with higher defects). Many individuals will require mobility supports such as leg braces, crutches or wheelchairs. More than 70% of children with myelomeningocele will require a shunt to be placed to relieve the pressure that builds up as a result of the accumulation of fluid around the brain (called hydrocephalus). This ventriculoperitoneal (VP) shunt, must remain in place for an individual’s entire life, and may occasionally become blocked, causing further complications and need to be replaced. Some affected children may have negative developmental and cognitive outcomes. One-third of adults with myelomeningocele require substantial lifelong daily support.
Treatment of spina bifida is available both before and after birth. The timing and choice of procedure depends on a number of important criteria, including gestational age at diagnosis, severity of the condition and the mother’s general health. Treatment of defects in-utero involves closing the spinal defect to prevent further spinal cord damage and may reverse the swelling on the brain.
The Management of Myelomeningocele Study (MOMS), a groundbreaking trial published in the New England Journal of Medicine in 2011, showed that, in babies who underwent the in-utero procedure:
- Brain malformations were reversed by one-third
- The need for walking aids or a wheelchair was halved
- The need for brain shunts was reduced by half
As a result, the Society of Obstetrics and Gynaecologists of Canada (SOGC) now requires that any pregnant woman whose fetus has been diagnosed with an open NTD be counselled about this treatment option.
In Canada, prenatal surgery is performed exclusively at the Ontario Fetal Centre.
Inclusion criteria for fetal myelomeningocele (fMMC) repair
- Singleton pregnancy
- Maternal age ≥ 18 yrs
- Open fetal spina bifida with upper level of the bony defect between T1 and S1. The lesion can extend below S1, but the highest level cannot be outside T1-S1 range.
- Chiari II malformation e. hindbrain herniation, which must be confirmed by ultrasound & MRI (MRI can be done locally or in Toronto).
- Normal karyotype. Normal CMA (chromosomal microarray) is also recommended.
- Gestational age at the time of fetal surgery ≤ 25+6
- Associated genetic or other unrelated major anatomical anomalies.
- Significant maternal co-morbidities, precluding safe surgery or anaesthesia
- Maternal BMI >40 kg/m2.
- Maternal: Insulin-dependent pre-gestational diabetes
- Abnormal placentation (praevia, abruption)
- Short cervix (<20mm) or cervical cerclage in-situor history of spontaneous preterm birth (<36+0 wks).
- History of classical uterine incision or hysterotomy or uterine anomaly
- Severe fetal kyphosis (>30°).
- RBC (Rh or Kell) alloimmunization or a history of fetal/neonatal alloimmune thrombocytopoenia (F/NAIT).
- Maternal HIV, Hepatitis-B or -C status positive.
- Early referral is necessary to allow for comprehensive work-up, multidisciplinary counselling and planning.
- Surgery is performed between 23 and 25 weeks gestation.
- Normal karyotype or microarray results are required prior to surgery.
- Fetal MRI and echocardiography will be organized at SickKids.
- After fetal myelomeningocele (fMMC) surgery, patients will remain in the hospital for at least one week.
- After discharge, patients will be required to stay within one hour of Mount Sinai for the first 3-4 weeks after surgery but will then be referred back to their local centre familiar with the management of spina bifida postnatally, for further ongoing care and delivery.
- Local patients will be followed and delivered at Mount Sinai Hospital.