Closed spinal dysraphism

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’. Spinal dysphraism is the term used to describe what happens when the spinal column (backbone) fails to form properly. This happens very early in pregnancy, before the end of the fourth week.

There are two types of spinal dysphraism: open, also called spina bifida aperta or myelomeningocele, or closed, also called spina bifida occulta.
In closed spinal dysphraism, the spinal cord (a tube-like structure containing nerves) and its coverings do not protrude through the back unlike in the open type. On its own, closed spinal dysphraism is unlikely to cause any problems, and many people have the condition without ever knowing it.

However, it can be associated with other conditions that could lead to problems with movement and bladder control. These include: thickened filum terminale, lipoma, split cord and dermal sinus.

Many of these, with the exception of dermal sinus can lead to ‘tethered cord’, which is the term used when the lower end of the spinal cord is attached to the lower bones of the spinal column rather than hanging freely as it should. Normally the spinal column grows more quickly than the spinal cord, so that by the time the baby is born, the spinal cord has moved higher up the spinal column.

If the cord is tethered, the spinal cord and nerves are stretched, reducing their ability to carry messages to and from the brain and causing pain. Growth spurts can stretch the spinal cord and nerves, causing problems with leg movement and bladder and bowel control. More detail about each of these follows.

Closed spinal dysraphism

Thickened filum terminale

The filum terminale connects the lower end of the spinal cord to the lowest bones in the spinal column (coccyx). In thickened filum terminale, the lower end of the spinal cord could be thicker than usual, and contain fat or muscle tissue as well as nerve tissue. This can cause problems such as tethered cord or scoliosis (side to side curvature of the spine).

Lipoma

A lipoma is a fatty lump that has formed beneath the skin. Some lipomas are in between the spinal cord and the spinal bones, but others may affect the spinal cord itself and the bone and tissue around the bottom of the spinal column. The lump puts pressure on the spinal cord, causing problems with messages being carried to and from the brain, and can lead to the cord becoming tethered.

Split cord

Sometimes, the spinal cord develops abnormally in the womb and becomes divided into two pieces lengthwise towards the bottom of the spine. The area between the split can be filled with bone or fibrous tissue. Split cord can occur on its own or in association with tethered cord.

Dermal sinus

This is a dimple in the skin in the middle of the lower back (or less commonly at the back of the head), which varies in depth from very shallow to very deep and connected to the spinal cord coverings. If the dimple is very deep, it can give a route for infection to get into the spinal cord and its coverings, which can lead to meningitis or abscesses. In some children, there is a birthmark or patch of hairy skin over the dermal sinus.

What are the symptoms of closed spinal dysphraism?

In many people, there may be no symptoms at all. However, a birthmark, hairy patch or dermal sinus in the lower back area may lead doctors to suspect that a child has closed spinal dysphraism. Other children may develop repeated bouts of meningitis for which no cause can be found or may have problems keeping dry (urinary incontinence) that cannot be explained.

If it not diagnosed until early childhood, the first sign might be weakness or unevenness of the legs or talipes (clubfeet) affecting one of both limbs. Back or leg pain might be a problem too. If these symptoms are due to a tethered cord they may get worse as the child grows.

Treatment by surgery tends to be suggested only when a child shows signs that his or her condition is getting worse, for instance, movement becomes more problematic or urinary incontinence is making everyday life more difficult or painful.

How is closed spinal dysphraism diagnosed?

Initial suspicions may be raised through clinical examination but imaging scans are used to confirm the extent of the problem. An ultrasound scan or magnetic resonance imaging scan are the usual methods used.

What causes closed spinal dysphraism?

We do not really understand what causes neural tube defects in general but we do know that folic acid can stop them happening.

How common is it?

Closed spinal dysphraism is much less common than the open type (myelomeningocele) but as it is a condition that can be undiagnosed in many people, we do not really know how many people are affected in the UK. The charity SHINE estimates that between five and ten per cent of people might have closed spinal dysphraism, of which only a small number develop problems.

How is closed spinal dysphraism treated?

If there are clinical symptoms that are getting worse, these may be reduced using surgery to release the tethered cord. This relieves pressure on the spinal cord and nerves and can improve leg symptoms in many cases. It is less successful in improving bladder and bowel problems but usually stops them getting any worse over time.

However, there are occasions where surgery is less successful and complete release of the tethered cord might not be possible. The spinal cord may also re-tether itself as the child grows so the procedure may need to be repeated at a later stage.

What happens before the operation?

You will have received information about how to prepare your child for the operation. On the day of surgery, the surgeon will explain the operation in more detail, discuss any worries you may have and ask you to give your permission for the operation by signing a consent form. Another doctor will visit you to explain about the anaesthetic. If your child has any medical problems, particularly allergies, please tell the doctors about these. Please also bring in any medicines your child is currently taking.

A physiotherapist will assess your child before the operation. This will give valuable information about how your child moves around and functions at home and at school. This helps us plan the support your child will need to return to what he or she was doing before the operation.

What does the operation involve?

While your child is under a general anaesthetic the surgeon will release the spinal cord from where it is tethered so that it can move as your child grows. If possible, the surgeon will reduce the size of a lipoma to relieve pressure on the spinal cord. After the operation, the incision on your child’s back will be closed and covered with a dressing.

Are there any risks?

The operation to detach a tethered cord is very specialised due to the complex arrangements of nerves in the area. There is always a risk that the nerves, or the spinal cord itself, could be damaged in the operation but if the surgeon believes that this may happen, he or she will stop the procedure. He will explain the problems that could occur in the unlikely event that the operation could result in damage to the nerves or spine and occasionally your child’s symptoms may become worse.

Leakage of cerebrospinal fluid (CSF) can cause vomiting or sleepiness but your child will be closely monitored in the days following the operation to reduce this. Lying flat for a few days after the operation also reduces this.

There is no guarantee that this operation will remove your child’s symptoms or even improve them. The aim of the operation is to stop them getting any worse. This operation tends to improve leg symptoms more frequently than bladder and bowel symptoms.

What happens afterwards?

Your child will come back from Theatres to the ward to recover. He or she may have a pressure bandage over the operation site and sometimes a lumbar drain, which is a plastic tube coming out from the wound to drain away any fluid that collects. Your child will need to lay flat for between three and five days after the operation to allow the area to heal well. Occasionally, the operation site might leak CSF from around the spinal cord or it might collect underneath the skin. This is sometimes unavoidable and should not cause any long-term problems.

The nurse caring for your child will make sure that he or she has regular pain relief and anti-sickness medicines and monitor your child closely for the first few days. Our ward play specialist will help you to keep your child amused, especially for the days when he or she has to remain lying flat. While your child is lying flat, we will encourage him or her to roll from side to side and move around in bed regularly. We can help him or her with this, as it can be a bit tricky immediately after the operation.

Your child will usually have a urinary catheter in place for a few days after the operation to drain urine, so avoiding the need to get up to go to the toilet. This will be removed when your child is up and about.

Once the doctors are happy that your child’s operation site is healing well, he or she can gradually sit up and start walking again. The physiotherapist will help with this, and we will make sure that your child has enough pain relief to make this as comfortable as possible. Even with pain relief moving around can be uncomfortable to begin with, as the muscles will be stiff and sore after lying down for a few days.

Your child’s legs might also feel weak and wobbly for the first few times standing up, but again this gradually improves over time. The physiotherapist will help your child with all these movements to make sure that he or she is safe at all times. Your child may feel a bit constipated after the operation. In most cases, this is due to being inactive for a while and so will improve as your child moves about more.

Once your child is moving about well, including going up and down stairs, he or she will be able to go home. The dressing will usually have been removed before going home but you may need to come back to the ward or visit your family doctor (GP) if stitches need removal. If your child still has some leg weakness, the physiotherapist may refer you to local services for ongoing help and support. He or she will also be able to advise about returning to school and normal everyday activities.

What is the outlook for children with closed spinal dysphraism?

Orthopaedic problems

In some cases, children may have developed leg and foot problems as a result of the closed spinal dysphraism. These can include clawing of the toes or very high arches, which in turn can lead to tightening of the Achilles tendon at the heel. This can affect one leg or both and if it is severe, we may refer your child to an orthopaedic surgeon for further treatment.

Where a child has scoliosis as a result of the closed spinal dysphraism, further treatment by an orthopaedic spinal surgeon may be required. Sometimes however, treatment of the dysphraism may reduce or even improve the progression of the spine curvature.

Bladder and bowel control

The nerves that control bladder and bowel function are contained in the lower portion of the spinal cord and so can be affected by closed spinal dysphraism. The degree to which bladder and bowel control is affected depends on the severity of the defect.

Problems associated with the bladder are largely due to incomplete emptying, which is caused by the messages from the bladder not being transmitted to the brain well enough. Incomplete emptying of the bladder can lead to urinary tract infections (UTIs) and backflow of urine towards the kidneys (reflux), sometimes severe enough to damage the kidney.

Signs of bladder problems include: urinary incontinence or dribbling, recurrent infections, bedwetting at night, needing to urinate frequently or having difficulties potty training. Bowel incontinence (soiling) is a less common problem, and rarely occurs if there are no bladder control problems. Early diagnosis and treatment can help reduce these problems but rarely solve them completely.

Movement

Closed spinal dysphraism can lead to muscle wastage on one side, affecting the buttocks and calf. This is caused by the muscles on one side being used more and therefore becoming stronger than the other, due to the stretching of the nerves leading away from the spinal cord when the cord is tethered. This can result in numbness, unbalanced walking, painless skin lesions, stiffness and pain in the lower limbs and back, sometimes relieved with odd postures or lying down.

The physiotherapist will advise you about strengthening these muscles and improving their function as much as possible. In some cases, your child will be referred to local services to continue these exercises at home.

What about future pregnancies?

There is now evidence that an adequate intake of folic acid can dramatically reduce the risk of neural tube defects occurring in future pregnancies. If you are planning a further pregnancy, we recommend that you 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.

Compiled by: 
The Neurosurgery Department in collaboration with the Child and Family Information Group
Last review date: 
November 2011
Ref: 
2011F0308