Spina Bifida: Myelomeningocele

What is myelomeningocele?

Myelomeningocele is a congenital birth defect (a condition that is present at birth) where the spinal cord and other deeper layers of the spine do not develop properly because of a gap in the baby’s backbone. This condition falls into a category of congenital spine defects that many doctors refer to as “spina bifida.” At MGfC, we think spina bifida can be a very confusing term – sometimes it refers to complicated conditions like myelomeningocele, while in other cases it refers to extremely mild forms of spinal problems that don’t cause any symptoms, such as spina bifida occulta. From now on in this article, we will use the term spinal dysraphism in place of spina bifida when discussing spinal problems generally. We will continue using the word myelomeningocele to refer to the specific type of spinal dysraphism discussed in this article. Read more about the difference between spina bifida and spinal dysraphism.

The spinal cord is a fragile bundle of nerves that plays an important role in sensation, movement of the limbs, control of the bowel and bladder and many other important functions. The spinal cord floats in a special liquid called cerebrospinal fluid (CSF), which is contained in a thin layer of tissue called the meninges. A layer of bone, called the backbone or spine, surrounds and protects both the meninges and spinal cord. In babies with myelomeningocele, these layers doesn’t close properly during early in fetal development, and a gap, or opening, is left in the baby’s spine, spinal cord, and/or meninges. Instead of being contained within the bony spine, the baby’s spinal cord protrudes through a fluid-filled sac that is visible outside the baby’s body, where it is exposed to the environment. Because the layers and the spinal cord don’t form properly, babies with myelomeningocele often have damage to their nerve tissue, which can result in lack of sensation and muscle weakness/paralysis in the area of the body below the defect. This may include bowel and bladder problems.

Children with myelomeningocele also often have problems with the formation of the brain. The gap in the baby’s spine allows some of the cerebrospinal fluid (CSF) that bathes the nervous system to escape the body, which can cause the brain to sink down into a lower position than what is normal. This displacement of the brain is called Chiari II malformation. The abnormal placement of the brain obstructs the flow of blood into the brain and can cause a buildup of CSF in and around the brain called hydrocephalus. Hydrocephalus can be dangerous because the extra fluid puts too much pressure on the delicate brain tissue. Most children with myelomeningocele will need to have shunt surgery or other types of surgery to divert this extra fluid into other parts of the body or through other passageways. Chiari malformations  are sometimes associated with other problems in the control of swallowing, breathing, and other functions.  Sometimes surgery is needed to take pressure off of the bottom of the brain by removing some bone at that site.

Myelomeningocele affects about 1 in 1000 babies and can cause a wide range of conditions requiring medical care. Despite this, many babies with myelomeningocele still go on to live long, fulfilling lives with the help of modern medical treatments.

What causes myelomeningocele?

Myelomeningocele and other types of spinal dysraphism occur when a cell structure called the neural tube fails to close while the baby is growing in the womb. During early fetal development, the collection of cells that eventually become your baby’s brain and spinal cord are supposed to fold into a tube shape. If the lower part of this tube doesn’t close correctly, the baby can develop a gap in part of the neural tube along the spine that causes different problems. For this reason, myelomeningocele is also known as a neural tube defect or NTD.

Most cases of myelomeningocele are not inherited (passed down in families) and occur randomly. However, parents that have had a baby with an NTD are at increased risk of having another baby with the same condition. 

In some cases, myelomeningocele is associated with a lack of folic acid in a mother’s diet during pregnancy, which is why doctors recommend women take folic acid vitamins if they are pregnant or thinking about getting pregnant. Myelomeningocele may also be caused by exposure to certain viruses or certain genetic factors.

What are the symptoms of myelomeningocele?

The primary finding in myelomeningocele is the presence of an abnormal-looking opening or fluid filled sac present on the baby’s back. Other symptoms may include

• Bowel and bladder problems, including incontinence and constipation
• Weakness and/or lack of sensation in the child’s legs and feet
• Inability for the child to move his or her legs
• Delayed developmental milestones

Myelomeningocele also can be associated with other complications, such as

• Hydrocephalus (water on the brain)
• Paralysis
• Chiari malformation (abnormal shape of the bottom of the brain)
• Other brain shape differences
• Learning disabilities

How is myelomeningocele diagnosed?

Most cases of myelomeningocele are discovered during a routine prenatal ultrasound. Other tests can be performed while the mother is pregnant, such as

• Blood test. A doctor will draw your blood to measure your AFP levels. AFP, which stands for alpha fetoprotein, is a protein released by your baby as he or she develops. AFP collects in the mother’s bloodstream at abnormally high levels when a baby has myelomeningocele. A blood test alone can only show an increased likelihood of your baby having spina bifida. Other tests are necessary to be sure of the diagnosis.
• Amniocentesis. In an amniocentesis, a doctor will use a needle to take a sample of the amniotic fluid that surrounds your baby inside the womb. The amniotic fluid sample can be analyzed to show whether or not the baby has myelomeningocele.

In some cases, myelomeningocele is not discovered until after the baby is born. Different imaging tests may be used in these circumstances to provide a diagnosis, such as X-ray and MRI.

How is myelomeningocele treated?

Babies with myelomeningocele will need regular ongoing support from a comprehensive and dedicated team of physicians and other healthcare specialists. There are a variety of different treatments available to help manage the child’s symptoms and maintain body functions. Many babies with the condition are delivered by C-section, to decrease the risk that their spinal cord will be damaged further during birth. Babies with myelomeningocele may also need to stay in the hospital’s NICU (neo-natal intensive care unit) for several days to weeks after they are born.

Myelomeningocele repair surgery

Babies born with myelomeningocele need to be treated with surgery, usually within the first several days of life. Myelomeningocele repair surgery is performed to close the gap in the lower back and prevent infection. First, your baby’s surgeon will close the meninges (thin membrane layers) that surround the spinal cord. The muscles of the back will then be reconstructed over the exposed area. Finally, the surgeon will close the opening in the skin of the lower back. This may require moving skin from another area on the baby’s back.

This type of surgery can only prevent further loss of function and cannot restore body functions that the baby did not develop prior to birth. 

Myelomeningocele repair surgery in utero

This type of repair procedure is called a fetal surgery. It is performed while the baby is still in the womb. In this surgery, the mother is put to sleep using anesthesia and the surgeon opens the abdomen and uterus to operate on the baby inside. This allows the surgeon to close the opening in the baby’s back before he or she is born, which in some cases can decrease the severity of symptoms and risk of complications after birth, but has its own set of risks. Your doctor can help you decide if this is an option you want to explore. 

Shunt surgery and other types of surgery

Many babies with myelomeningocele develop hydrocephalus (fluid build-up in the brain) shortly after birth. To treat this complication, your baby’s surgeon will often insert a shunt, which is a small tube that threads from the fluid spaced inside the brain into another area of the body, usually the abdominal cavity. The tube helps drain the extra fluid from around the baby’s brain into an area such as the abdomen, where it can be safely absorbed by the body. This prevents too much pressure from building up and damaging the brain tissue. The tube is entirely under the skin and doesn’t show on the outside.

In some children, a surgical opening can be made within the brain through a small camera, or endoscope, that allows fluid to circulate more normally.  This approach can sometimes treat the fluid buildup without the child needing a shunt.  While this is used more often for older children, some babies with myelomeningocele may be candidates for this surgical approach. Your doctor will talk with you about what’s best for your baby. 

Physical therapy for myelomeningocele 

Some children with myelomeningocele have trouble walking on their own, because the nerves that control the muscles in their legs don’t work properly. Tools like leg braces and crutches allow some children with myelomeningocele to walk more independently.  Because the legs and feet may be shaped differently, some children will benefit from physical therapy or orthopedic surgery to help their legs and feet work most effectively.

What is the outlook for my baby with myelomeningocele?

Myelomeningocele is a complex condition that requires long-term care tailored to your child’s unique needs. At MGfC, you and your child will work with a caring team of physicians from many of our different high-quality pediatric specialties, including urology, orthopedics, neurosurgery and general medicine. Our doctors will help manage your child’s existing symptoms and address any new medical problems that may arise throughout your child’s life.