What is Spina Bifida?
Spina bifida is a type of neural tube defect (NTD). It is not a life threatening conidition, but it can result in significant and varying disabilities. There are a number of factors that affect the degree and type(s) of disabilities.
The neural tube develops into the spinal cord and brain very early in pregnancy. It forms and closes the spinal cord and nerves within protective vertebrae (bones). When there is an NTD present, the spinal column does not close completely as it is developing. This occurs at around 23 days gestation.
There are different types of neural tube defects; open and closed.
- Open means that the nerves of the spinal cord are not protected by skin and may bulge out of the spine into a sac on the back (i.e., myelomeningocele, and meningocele)
- Closed means that the skin has formed over the spine, but nerves may still be affected. As there is no open membrane, these conditions require less urgent surgical intervention after birth (i.e. lipomeningocele and spina bifida occulta)
Types of Spina Bifida
There are different types of spina bifida, each name describes which part of the spine/brain is affected. The names can be long and scary and hard to pronounce. If you know where the words come from, it can help to understand the medical terms.
The four main types of spina bifida are: myelomeningocele, meningocele, lipomeningocele, and occulta
- “myelo” is the spinal cord
- “meninges” is the protective covering of the spinal cord
- “cele” identifies swelling, or a sac
- “lipo” means fat
- “occult” means hidden
Myelomeningocele (pronounced milo-my-ninja-seal) is when the spinal cord and protective covering (meninges) both come out of the opening in the spine.
Meningocele (pronounced my-ninja-seal) is when the meninges, but not the spinal cord, come out of the opening in the spine.
Lipomeningocele (pronounced lie-po-my-ninja-seal) is when fat tissue is caught in the meninges and comes out of the opening in the spine. It is covered in skin and does not require surgery at birth.
Spina bifida occulta (pronounced oh-cull-tah) is when there is an opening in the spine, but nothing comes out. It is skin covered and may not be diagnosed at birth.
Myelomeningocele (pronounced milo-my-ninja-seal) is when the spinal cord and protective covering (meninges) both come out of the opening in the spine.
Meningocele (pronounced my-ninja-seal) is when the meninges, but not the spinal cord, come out of the opening in the spine.
Lipomeningocele (pronounced lie-po-my-ninja-seal) is when fat tissue is caught in the meninges and comes out of the opening in the spine. It is covered in skin and does not require surgery at birth.
Spina bifida occulta (pronounced oh-cull-tah) is when there is an opening in the spine, but nothing comes out. It is skin covered and may not be diagnosed at birth.
Myelomeningocele (pronounced milo-my-ninja-seal) is when the spinal cord and protective covering (meninges) both come out of the opening in the spine.
Meningocele (pronounced my-ninja-seal) is when the meninges, but not the spinal cord, come out of the opening in the spine.
Lipomeningocele (pronounced lie-po-my-ninja-seal) is when fat tissue is caught in the meninges and comes out of the opening in the spine. It is covered in skin and does not require surgery at birth.
Spina bifida occulta (pronounced oh-cull-tah) is when there is an opening in the spine, but nothing comes out. It is skin covered and may not be diagnosed at birth.
Spina Bifida Levels
When the doctors look at the scans they will estimate a 'level’ of spina bifida. The 'level' is the location of the opening or lesion on the spine, and what nerves may be affected.
The spinal cord is actually a collection of nerves. Nerves tell your body what to do, how to move, and what to feel. If nerves are damaged, it is difficult for the brain to tell the body to move (motor control), and the body to tell the brain what it feels (dermatone).
The location of the lesion (identified by one or more letters and numbers) will guide the doctors as they attempt to estimate what your child may feel and how much your child may be able to move.
The label of the lesion is not an absolute determinant of outcomes for a child or adult with spina bifida. As time goes on, you and your child will learn what is possible and what adaptations will help them move about and explore the world.
The spinal cord is divided into 4 regions, and each region is identified by a letter.
- Cervical - C
- Thoracic - T
- Lumbar - L
- Sacral - S
The most common areas for spina bifida (the lesion) to occur is in the lumbar and/or sacral region.
Each region is then identified by a specific vertebrae number. A vertebra is a bone that makes up a part of the spine. Vertebrae numbers start at the neck and count down towards the tailbone.
- The cervical region has 7 vertebrae, C1 – C7
- The thoracic region has 12 vertebra, T1-T12
- The lumbar region has 5 vertebrae, L1-L5
- The sacral region has 5 vertebrae, S1-5
- The coccyx is your tailbone
Motor control is how the nerves tell the body to move; different nerves control different muscles. Movement uses many different muscles, some might be strong, some might be weak.
A dermatome is an area of skin and its nerve tissue that tell the brain what to feel and how to feel touch, temperature and pain. When nerves are affected, the feeling of touch, temperature, and pain is decreased or absent.
Spina Bifida and the Brain
Spina bifida can also affect the brain. This is most common in babies affected by an open NTD, such as myelomeningocele. Due to the opening in the spine, there is a pull on the brain as it is developing. This blocks the normal flow of the fluid around the brain, called cerebral spinal fluid.
Hydrocephalus and Arnold-chiari 2 malformation are the effects of spina bifida on the brain.
Hydrocephalus affects the ventricles, while Arnold-chiari 2 malformation affects the cerebellum of the brain.
Recent studies have shown that fetal surgery can potentially improve brain-related outcomes in some cases. When children who met a specific criterion had fetal surgery, there was a significant decrease in treatment of hydrocephalus (the need for shunt decreased from 85% to 40%), and some improvement in Arnold-chiari 2 malformation, (absence of hind brain herniation at 1 year was 4% in postnatal group compared to 36% in fetal surgery group). It was also shown that fetal surgery can result in slight improvements in a child’s mobility.ii
Hydrocephalus
Cerebral spinal fluid (CSF) is fluid that is found in the brain and the spinal cord. Its role is to protect, nourish, and be the cleaning system for the brain.
In the center of the brain, there are fluid filled chambers called ventricles. The space in the ventricles is measured in “mm” on an ultrasound. These ultrasounds can be done while you are still pregnant (fetal ultrasound) or after your baby is born (head ultrasound).
When there is too much CSF in the ventricles, it is called hydrocephalus, which literally means water in the brain.
- “Hydro” means water
- “Cephalus” means head
On a head MRI, this is what hydrocephalus looks like:
Normal MRI
Hydrocephalus
In the first year, your baby’s skull is still developing and there are soft spots or areas where the bone has not yet filled in (fontanels). This lets the brain grow in the first year. With hydrocephalus, your baby’s head size may grow more than expected as the skull is made to enlarge to accomodate the growth of the ventricles.
The neurosurgeon will review all of the measurements and progression with you in their treatment recommendations.
Treatment
There are different treatments for hydrocephalus to help the body absorb the extra fluid in the brain.
- A shunt is a tube that is surgically inserted into the ventricle in the brain in order to drain the extra fluid and direct it to another part of the body to be absorbed (most commonly the belly). The shunt remains in the body, and may need to be replaced as the child grows or in case of infection/blockage. This is the most common treatment.
- Think of this like a straw to take extra fluid from one place to another.
- A recently introduced surgical alternative is an operation called Endoscopic Third Ventriculostomy (ETV) which creates a new path for fluid to drain within the ventricle system. It is most effective when combined with a choroid plexus cauterization (CPC) which is done at the same time (ETV–CPC)iii. This involves destroying some of the tissue that makes CSF, to decrease the rate of CSF production. The main benefit of this surgery is that there is no artificial material left in the body, however it is not always successful.
- Think of this as making a bigger bathtub (ETV) and turning down the tap (CPC) so that the water drains out and doesn’t overflow.
- Sometimes routine monitoring is all that is needed.
Your child’s neurosurgeon is the specialist to ask about these treatment options.
Fetal surgery has decreased the incidence of shunts to treat hydrocephalus in kids with spina bifida: 80% without fetal surgery, and 40% after fetal surgery. Resulting in reduced rates of surgical intervention for some kids.iv
Arnold-Chiari 2 malformation
Arnold-chiari (prounounced key-yar-ree) is named after the researchers who discovered this type of brain malformation. Type 2 is associated with open NTD spina bifida. It is medically called “hindbrain herniation” and it means that the cerebellum, the bottom part of the brain, is being pulled down through the base of the skull and into the top of the spine.
Often they will see this on your fetal ultrasound and use words like “banana sign” or “lemon sign” which simply describe how the radiologist sees the ultrasound findings. Some children may have symptoms of chiari 2 malformation, and some children may not.
Your child’s neurosurgeon is the expert and will be able to answer questions regarding this diagnosis.
References
i Holland Bloorview. (1998). Understanding Spina Bifida Booklet, 21.
iiAdzick NS, Thom EA, Spong CY, Brock JW 3rd, Burrows PK, Johnson MP, Howell LJ, Farrell JA, Dabrowiak ME, Sutton LN, Gupta N, Tulipan NB, D’Alton ME & Farmer DL. (2011) A Randomized Trial of Prenatal Versus Postnatal Repair of Myelomeningocele. New England Journal of Medicine. 364(11):993–1004
iiiKulkarni AV, Schiff SJ, Mbabazi-Kabachelor E, Mugamba J, Ssenyonga P, Donnelly R, Levenbach J, Monga V, Peterson M, MacDonald M, Cherukuri V & Warf BC. (2017). Endoscopic Treatment versusu Shunting for Infant Hydrocephalus in Uganda. New England Journal of Medicine. 377:2456-2464
ivSaadai P & Farmer DL. (2012). Clinics in Perinatlology: Fetal Surgery for Myelomeningocele. Clinical Perinatology; 39(2): 279-288