Myelomeningocele is a type of spina bifida. This is when the neural tube has failed to close and the neural tissue is exposed on the baby’s back. The myelomeningocele will look like a sac sticking out from a baby’s back.
In early development, the brain and spinal cord start as a tube-like structure called the ‘neural tube’ that is open at either end. These openings close within the first weeks of pregnancy, and the neural tube continues to grow and fold, eventually forming the brain and spinal cord.
If the tube fails to close properly, this results in a group of problems called ‘neural tube defects’. There are two types of neural tube defect: open, also called spina bifida aperta or myelomeningocele, or closed, also called spina bifida occulta.
This information explains about the open myelomeningocele type, which accounts for 75 per cent of all cases of spina bifida.
In myelomeningocele, the neural tube has failed to close and the neural tissue is exposed at a place on the baby’s back called the ‘neural placode’. This most commonly happens in the baby’s lower back just above the bottom, but could occur anywhere along the spine. The myelomeningocele will look like a sac sticking out from the baby’s back.
What causes myelomeningocele?
We do not really understand what causes neural tube defects in general, but we do know that folic acid can stop them happening in future pregnancies.
How is myelomeningocele treated?
Without the protective covering of skin, the spinal cord will become further damaged, spinal fluid often leaks from the area and there is a very high risk of infection. Surgery is usually recommended within the first few days of life.
The aim of surgery at this stage is to put the spinal cord back into the spinal canal and repair the defect in the back so that the area is covered with normal, healthy skin.
Before surgery, the affected area is covered with a dressing and the baby will be nursed on their front. A number of specialists will visit to examine the baby, including a neurosurgeon, physiotherapist, paediatrician, orthopaedic surgeon and anaesthetist.
After the operation, the infant will be nursed on our neurosurgical ward, still on their front for most of the time, although parents will be able to feed their baby by breast or bottle and pick up the child as normal.
The physiotherapist will see the child after the operation. They will assess how much strength the baby has in each muscle group and measure their sense of feel. When taken together, muscle strength, sensation and reflexes give us a picture of how well the messages are getting from the brain to the arms and legs via the spinal cord.
The physiotherapist will also give advice on how to position and handle the child to stretch out tight muscles and to help with normal development. They may also refer a child to local physiotherapy services who can continue to see the child and monitor their development. They will also monitor the movement in the child’s muscles and joints and may refer them to an orthopaedic doctor at a local hospital.
Once the baby is recovering well, they will be able to go home. We will need them to come back to the ward between 10 and 14 days after the operation, so that we can check the operation site, carry out an ultrasound scan of the baby’s head and measure their head circumference.
Four to six weeks afterwards, they will need to come to clinic for a further check up appointment.
What problems can myelomeningocele cause?
There are a number of problems that might face a child born with myelomeningocele. However, we want to emphasise that these vary a great deal from child to child and also may show up at different times during a child’s development.
Some degree of bladder problem is the most commonly occurring problem for children with myelomeningocele.
However, it is not usually a concern in the first year or so before any baby is potty trained. Many children with myelomeningocele will fail to develop normal bladder control, but with treatment from a urologist, most children can become ‘dry’. Urine infections can be risk for children with myelomeningocele, owing to their bladder control problems.
A urologist will usually visit soon after birth and tests and investigations will start straightaway. Bowel continence can also be a problem. Medicines and sometimes surgery may be needed in the longer term.
The circulation of cerebrospinal fluid (CSF) is often disturbed in children with myelomeningocele. Either at birth or in the days and weeks following surgery, fluid may start to build up within the brain. This is called hydrocephalus and can result in increased pressure in the brain.
If this occurs, an operation to place a shunt tube to divert the excess fluid from the brain to the abdomen is needed. This operation is needed in about 60 per cent of children with myelomeningocele.
Arnold Chiari malformation
This is present in almost all children with myelomeningocele. It mainly involves the lower part of the brain, but the anatomy of the whole brain is affected. Many of the nerves that control the heart, breathing and blood pressure, and help control swallowing, sneezing and coughing can be involved.
When Arnold Chiari malformation is present, the brainstem is elongated and displaced into the opening of the base of the skull and into the top of the spinal canal. It is often kinked. The brainstem, cranial nerves and lower portion of the cerebellum (back of the brain) may be stretched or compressed. This means that any of the functions controlled by these areas may be affected.
Many people with Arnold Chiari malformation have no obvious symptoms. In babies, the most common symptoms are a weak or absent cry, stridor (noisy breathing), arching of the neck, breathing problems, colour change, failure to thrive and feeding or swallowing difficulties.
If any of these symptoms is present, medical advice is needed. Treatment may involve removing a small amount of the bone around the neck and base of the skull to relieve pressure on the brainstem.
Myelomeningocele affects each child differently, and how each child moves around will vary too. Some children will need splints or walking aids, and others may move around more easily in a wheelchair. The consultant will speak with parents about how their child’s condition will affect their mobility.
What is the outlook for children with myelomeningocele?
The outlook for children with myelomeningocele has improved dramatically in recent decades. Intellectual prognosis is very good for the majority of children, most of whom will go on to full time education. Recreational and employment opportunities are better now than at any time in the past.
In order to fulfil potential and avoid unnecessary complications, a child will need follow up care from a multidisciplinary team throughout childhood. To enable this, the baby will be referred to your local hospital before you leave Great Ormond Street Hospital (GOSH). This is important so that a consultant paediatrician and other relevant local teams are involved in the child’s ongoing care.
What about future pregnancies?
There is now evidence that an adequate intake of folic acid can dramatically reduce the risk of myelomeningocele occurring in future pregnancies.
If someone is planning a further pregnancy, we recommend that they take 4mg of folic acid each day for at least three months before conception and for the first three months of pregnancy. This dose is higher than the standard recommendation for women who have not previously had a child with spina bifida.
If you have any concerns about future pregnancies, please talk to us as we can arrange a consultation with a genetic specialist for you.