What is spina bifida?
The spinal cord is a thick bundle of nerves that carries messages between the brain and the rest of the body. It floats in a liquid called cerebrospinal fluid (CSF). This liquid nourishes and protects the brain and spinal cord. The CSF is covered by a lining made of three thin layers called the meninges. This lining is normally protected by the bones of the back (the vertebrae).
In people with spina bifida, the bones that protect the spinal cord have not formed completely while the baby is developing in the mother’s womb. This leaves the lining, the CSF, and the spinal cord unprotected. This happens very early in pregnancy.
The central nervous system starts to develop in week five of pregnancy. At that time, a thickening of cells called the neural plate forms, which folds in on itself to create what we know as the neural tube. One end of the neural tube will form the brain, and the remainder of the neural tube will form the spinal cord. In week six, openings in the neural tube close. If these openings do not close properly, abnormalities called neural tube defects can form. These defects are rare, but they account for most of the abnormalities of the brain and spinal cord.
This animation depicts the following process: At the end of week five, a set of cells in the ectoderm layer starts to become taller. This set of cells forms a structure called the neural plate. A groove forms along the middle of the neural plate, which is flanked on either side by two folds. The folds fuse together to begin formation of another structure called the neural tube. The neural tube will become an integral part in the development of the central nervous system. The neural plate will give rise to other types of cells, which will eventually form the nerves extending from the brain and spine, and other structures.
Spina bifida can happen anywhere along a baby’s back between the head and the hips. It happens most often in the lower back. This area is called the lumbar or lumbosacral spine.
Children with spina bifida may have health problems because of this condition. They may experience changes or loss of feeling in their legs, have decreased movement of their legs or not be able to move their legs at all. They may also have problems with their bladder and bowel function.
About 2.6 in every 10,000 babies are born with some form of spina bifida.
The four main types of spina bifida
There are four main types of spina bifida:
- spina bifida occulta
- lipomyelomeningocele
- meningocele
- myelomeningocele
“Meningo” refers to the lining of the vertebral canal. “Myelo” refers to the spinal cord itself. “Cele” means something bulging out.
Spina bifida occulta
Spina bifida occulta is the mildest form of spina bifida. It occurs when a small section of the outer part of the vertebrae (the bones of the spine) have not completely closed, leaving an opening. In this type of spina bifida, the spinal cord and its coverings (the meninges) are usually not damaged and they do not protrude or bulge through the opening. There may be a dimple, tuft of hair, birthmark or fatty bulge at the site of the defect. This type of spina bifida may not be detected before birth. Many people may have this type of spina bifida and not be aware of it.
Lipomyelomeningocele
A lipomyelomeningocele (ly-po-my-low-meh-nin-go-seal) is a form of spina bifida where the outer part of the vertebrae have not completely closed, leaving an opening. Some abnormal fatty tissue pushes through the opening and may cause compression of the nerves.
Meningocele
A meningocele (meh-nin-go-seal) is a more severe form of spina bifida. It occurs when the outer part of the vertebrae have not completely closed, leaving an opening. The spinal cord itself may not be affected, but its protective coverings (the meninges) may be damaged and pushed through the opening to form a sac containing CSF. This sac is often covered with skin.
With a meningocele, the spinal cord stays inside the back where it belongs. This means that children with a meningocele may have normal movement and normal feeling in their legs and feet.
Myelomeningocele
A myelomeningocele (my-low-meh-nin-go-cele) is the most severe form of spina bifida. It occurs when the outer part of the vertebrae have not completely closed, leaving an opening. With a myelomeningocele, both the covering of the spinal cord (the meninges) and the spinal cord itself are pushed out through the opening. Usually they protrude into a covered, fluid-filled sac that has a very thin membrane and can easily split, exposing its delicate contents.
Because part of the spinal cord bulges into the sac, the spinal cord fails to develop properly and nerves are damaged. Most children with a myelomeningocele will have some difficulty with movement and feeling in their legs and feet, and may be paralyzed.
Causes of spina bifida
All of the causes of spina bifida are not known but there are genetic, environmental and nutritional risks linked to spina bifida.
- Some spina bifida is found in families, meaning there may be a genetic link.
- What you eat during pregnancy may have an impact on healthy growth of the spinal cord.
- Some medications that interfere with the body’s ability to use folate and folic acid could increase risk.
- Women with diabetes whose blood sugars are not well controlled have a higher risk.
- Increased body temperature (for example from using a sauna or hot tub) in early weeks of pregnancy may increase risk.
Spina bifida and other neural tube defects are less likely to occur when women get enough folic acid. These defects occur in early pregnancy, often before many women even know they are pregnant. If there is any possibility of becoming pregnant, it is important to have a well-balanced diet rich in folic acid. If you are planning to become pregnant, it is essential that you begin taking folic acid daily, at least three or four months before you start trying to conceive. Talk with your doctor about the right dosage for you. The usual recommended dose is 400 micrograms (mcg) of folic acid a day. Often this can be found in a prenatal vitamin. If you have had a pregnancy affected by spina bifida, or a family history of spina bifida or are taking certain medications, you may require a higher dose of folic acid.
Diagnosis of spina bifida
Spina bifida can be diagnosed during pregnancy or after the baby is born.
During pregnancy
There are tests that can be done during pregnancy that can indicate if the baby has a high chance of having spina bifida.
- Alpha-fetoprotein (AFP) blood test – AFP is a protein made by unborn babies. AFP crosses from the baby through the placenta to the mother. A test is done that measures AFP levels in the mother's blood. If there are high levels of AFP in the mother's blood this might mean that the baby has spina bifida.
- Ultrasound – this is a common test during pregnancy that allows health-care providers to see images of the unborn baby. In some cases, an ultrasound can show if the baby has spina bifida.
- Amniocentesis – this is a test that takes a small sample of amniotic fluid from the mother’s womb. If this fluid has a higher than average level of AFP then the baby might have spina bifida.
- Fetal MRI – if initial tests suggest there is a high chance of spina bifida then a fetal MRI can be done. This is an MRI that is done on the pregnant mother to assess the unborn baby.
Spina bifida occulta may not be diagnosed until late childhood, adulthood or may not be diagnosed at all.
Treatment of spina bifida
Meningocele where only the meninges are pushed through the opening and myelomeningocele where the meninges and spinal cord are pushed out through the opening are both treated with surgery. Older infants and young children with lipomyelomeningocele may require surgery if they develop symptoms. Spina bifida occulta does not usually require treatment.
To learn more about the treatment of spina bifida please read Spina bifida: Treatment and caring for your child after surgical repair.
Health problems linked to or caused by spina bifida
Every child with spina bifida is different with their own medical, mobility and learning challenges. Some children may only be mildly affected while others may have more severe disabilities. Being born with spina bifida brings life-long challenges. Your child’s health-care team will work together with you to help your child achieve their greatest potential.
The following health issues are common for children with spina bifida.
Hydrocephalus
About 80 percent of babies born with spina bifida, primarily those with myelomeningocele, will also have hydrocephalus. Hydrocephalus is an abnormal build-up of CSF in the ventricles inside the brain.
Chiari malformation
Nearly all babies born with myelomeningocele have a Chiari malformation type 2. This is when the lower part of the brain (the brainstem) sits too low in your child’s upper spine area. Some children with Chiari malformation type 2 may have feeding problems (for example, weak suck when feeding, gagging, choking, trouble swallowing), breathing trouble and some may have weakness of the arms. Surgery may be required to decrease the pressure on the lower part of the brain.
Leg function (movement) and sensation (feeling)
In children with spina bifida, the nerves in the spinal canal are often damaged or improperly formed, and therefore they may not able to control the muscles properly or sometimes feel properly. Some children may be paralyzed, not able to move their legs at all, while others can stand and walk to some extent.
Muscles and bones
Muscles and bones may also be affected by spina bifida. A baby with spina bifida may be born with clubfoot, this is when the baby's feet are turned in at the ankle.
The baby's hips may also be affected as different muscles may be stronger than others interfering with how the hips move and function. This can cause dislocation of the hip.
Muscles around the spine may also be affected. Any difference in muscle strength can affect the position of the spine and cause an abnormal curve.
If your child has clubfoot or any leg bone issues an orthopaedic surgeon will speak to you about options for correcting this in the future.
Bladder problems
With spina bifida, the nerves that tell the bladder to empty and release urine (pee) are often weak or not working. This means you may have to help your baby to pee and empty their bladder. When your baby is born, a tube or catheter will be put inside their bladder through the urethra every few hours to see if they can pee on their own and empty their bladder. The urethra is the tube inside the body that carries urine from the bladder to the outside of the body. If your baby is unable to fully empty their bladder, they are at risk for an infection and possibly damage to their kidneys. You may need to learn how to empty your baby’s bladder using a catheter before you can take them home. Instructions for boys and girls are slightly different. A member of the urology team will talk to you about this.
Bowel problems
Sometimes the nerves that make the bowels move are weak or not working. The nurse will be assessing how well your baby’s bowels move. The nurse can teach you how to help your baby’s bowels move better and how to protect your baby’s skin around their anus.
Latex allergies/sensitivity
Babies with spina bifida have a high risk of developing a latex sensitivity or allergy. It is important to make sure that products such as gloves, catheters and soothers do not contain latex.
Tethered cord
In children with spina bifida, sometimes the spinal cord gets stuck at the site where the vertebrae have not closed completely. This is called a tethered cord.
Looking ahead
Babies born with spina bifida require ongoing assessment as they grow and develop. They will be followed by a number of different medical teams. Some children may be in special spina bifida clinics.
Resources
Spina Bifida and Hydrocepahlus Association of Ontario
http://www.sbhac.ca
Holland Bloorview Kids Rehabilitation Hospital
http://www.hollandbloorview.ca/
Public Health Agency of Canada. (2013). Congenital Anomalies in Canada 2013: A Perinatal Health Surveillance Report. Retrieved from http://publications.gc.ca/collections/collection_2014/aspc-phac/HP35-40-2013-eng.pdf.