Spina bifida occulta is common. Two studies undertaken in Great Britain in the mid 1980s suggest that 22% or 23% of people have spina bifida occulta. Even though there is a very slightly increased chance of a slipped disc, very few people with spina bifida occulta will ever have any problems because of it. If a person has no symptoms from spina bifida occulta as a child, then it is unlikely that they will have any as an adult.

Most people will not even be aware that they have spina bifida occulta unless it shows up on an X-ray which they have for some unrelated reason. It is usually just a small part of one vertebra low in the back which is missing. See the diagrams below that show cross sections of one vertebra.

Image of normal spine

Image of spine with spina bifia occulta

 

However, for some people (about 2% of those who have spina bifida occulta) there can be other problems. These problems arise because there are other things involved around the area where the vertebra has not formed properly. For this small percentage of people the problem with the spine can also be more extensive than just a small piece of missing bone. More than one vertebra can be involved and these vertebrae may be malformed.

Some of the other things which can occur around this site and affect a person’s functioning are:

• Distortion of the spinal cord and the nerve roots coming from the spine by fibrous bands or adhesions
• Fatty tumours in the spine, under the skin or in surrounding tissues
• Cysts in the skin or just under it
• Cysts filled with cerebrospinal fluid in the spine (syrinxes)
• Divisions in the spinal cord
• Spinal cord tethered or held down at the site (unable to move freely in the spinal canal)

To avoid confusion, the term often used to for spina bifida occulta with these associated problems is occult spinal dysraphism (OSD).

In addition to these structures which are usually hidden from view, there are a number of signs which may appear on the skin (cutaneous signatures) and give a clue to the underlying problems with the central nervous system. These signs can appear on their own but quite often they appear in combination. Some common ones are:

• An abnormal hair growth over the thoracic or lumbar spine
• A dermal sinus or small tract which leads from the skin surface down through to the spinal cord. Blind sinuses or pits which do not lead into the spine are common in newborns especially in the crease of the bottom and do not indicate underlying problems.
• A fatty mass (lipoma) just under the skin
• A rudimentary tail
• A capillary haemangioma (stork bite) over the lower spine. Haemangioma over the back of the head are more common and do not indicate underlying problems.

A word of warning: This sounds as if there is clear difference between spina bifida occulta and occult spinal dysraphism (OSD). In practice, this is not always the case. The best test available at the moment is the MRI (Magnetic Resonance Imaging), but sometimes it is not easy to determine whether or not there is any neural (nerve) involvement. This difficulty is also of significance when looking at genetic issues, which is dealt with further on.

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How can occult spinal dysraphism affect functioning
Because the spine and the nerve roots at the site of the lesion are affected, in theory any problem from the waist down can be due to OSD. Depending on the amount of neural involvement, symptoms can be absent, minimal, or severe. Symptoms can include:

• Weakness or sensory loss in the legs, feet
• Leg length difference
• Foot deformity
• Problems with gait (walking)
• Bowel or bladder infection or incontinence
• Constipation
• Scoliosis (sideways curvature of the spine)
• Back pain
• Continence problems

Continence problems may present as

• Bedwetting which persists well into childhood
• Lack of awareness of need to pass urine until it is urgent
• Inability to hold on, even for a few minutes
• Dribbling of urine between visits to the toilet
• Recurrent urinary tract infections
• Constipation

For parents of young children with these problems, it is important for you to:

• Not lose patience with your child. Discipline or behaviour management rarely solves this problem.
• The self-esteem of your child is of paramount importance.
• Try to establish a toileting routine eg toileting first thing in the morning, at morning tea, lunchtime, after school, after dinner and just before bed. Ensure the last drink is several hours before bedtime if possible. Adequate fluids throughout the day are essential though.
• Talk to your child’s school. Let them know about your child’s toileting needs, so that the school can accommodate them.
• Ask your GP for a referral to a urologist (a specialist in urinary problems).
• Talk to a Continence Adviser regarding continence aids.

For constipation, seek advice on management from a Continence Adviser. This problem can betreated more effectively if treated early. A well-balanced high fibre diet is important.

Lower limb problems
Most children and adults with OSD have no orthopaedic (muscle and bone) problems. When problems do manifest though, a GP should be consulted who may refer to an orthopaedic surgeon.

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Back pain
Back pain may be a significant problem for people with OSD. It is sometimes present even in young children. It may be difficult or impossible to say that OSD is actually causing the pain.

Back pain is very common in our society. Many people suffer back pain for a great variety of reasons and those reasons may be present with or without OSD. For a person experiencing back pain it is appropriate to look at what other factors may be influencing the pain. The fact that a person has OSD cannot be changed, but many other factors can.

It is important to be aware of good back care eg correct lifting methods, good posture, appropriate exercise etc. A physiotherapist can give advice in these areas.

Tethering of the spinal cord
The normal spinal cord moves freely in the spinal canal. However sometimes in OSD, the cord becomes tethered or stuck down. This can cause stretching of the cord and affect the blood flow to the area, especially during times of rapid growth.

Some of the symptoms of a tethered spinal cord are:

• Increased weakness or loss of muscle function
• Increased muscle tone
• Deterioration in gait
• Worsening of bladder function
• Progressing scoliosis
• Back pain

All of these symptoms can have other causes and should be investigated. The spinal cord can be tethered with no symptoms. If it is warranted, an operation can be performed by a neurosurgeon to ‘detether’ the spinal cord.

This procedure will usually not restore lost functioning, but in most cases it is able to halt the worsening of symptoms.

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Corrective surgery
OSD develops during the first month of pregnancy and cannot be corrected. However, surgery can assist with some aspects. Apart from spinal cord detethering, surgical procedures

• can remove fat or fibrous tissues which are affecting the
• functioning of the spinal cord,
• can drain syrinxes or cysts in the spinal canal to reduce pressure on the spinal cord
• can be performed on the legs or feet to improve their functioning
  

Genetics
The cause of spina bifida and OSD is not well understood. There seems to be a combination of genetic and environmental factors which give parents an increased risk of having a child with a neural tube defect.

In Australia, neural tube defects affect 1 pregnancy in 500. It is well known that the risk of a child being born with a neural tube defect such as spina bifida is increased if there is a close family history of neural tube defects (anencephaly, spina bifida).

For a first-degree relative ie a parent or sibling the risk is about 1 in 25.

What is not so well known though, is that the risk is also increased if the close family history includes OSD. Research is not yet clear on whether the family occurrence of OSD predisposes to an increased risk of a child being born with any neural tube defect not just OSD.

Thus people who have occult spinal dysraphism or with a close family history of it should seek the advice of a genetic counsellor if they are contemplating having children.

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Prevention
One factor which influences the risk of having a child with spina bifida is the amount of folic acid in the mother’s diet. Folic acid is a water-soluble vitamin found in many fruits, leafy green vegetables, cereals and legumes.

A diet rich in folate (the naturally occurring folic acid) or the taking of folic acid supplements of 0.5 mg. each day for the month before and the first three months of pregnancy can reduce the risk of neural tube defects by up to 70%.

However, people with a close family history of neural tube defects, including OSD have a higher risk of having a child with a neural tube defect. Women in high-risk groups like this need to take a higher dose (5 mg.) of folic acid. Higher dose folic acid supplements are available from pharmacies.

NOTE: It is impossible to get 5 mg. of folic acid from eating foods high in (or even fortified with) folate.
It is known that in our society, only half of all pregnancies are planned. By the time a woman discovers that she is pregnant, any problem with the development of the neural tube will already have taken place. By then it is too late for folic acid to have any effect. So, it is advisable for all women who could become pregnant to take a folic acid supplement. More information

Genetic Counselling
Genetic counselling may involve the diagnosis of an inherited condition, the provision of information about a particular condition including the chances of having a child with that condition or supportive counselling by a team of health professionals. For more information on genetic counselling please contact the Clinical Genetic Counselling Service in you state.

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