AN INTRODUCTION TO SPINA BIFIDA

What is Spina Bifida?

Spina Bifida is a fault in the spinal column in which one or more vertebrae (the bones which form the backbone) fail to form properly, leaving a gap or split. To help understand what it is, let us explain about the composition of the nervous system.

The central nervous system

The central nervous system is the mechanism which enables us to move, feel, taste and see. It is an extremely complicated and potentially vulnerable system. Its most important component is the spinal cord. This is the main communication system for the body and, because it is so vital, it has to be adequately protected.

The spine

The spine is made up of 33 bones or vertebrae. The vertebrae have two main functions. One is to provide anchorage for muscles so that we can move as we dictate to those muscles. The other is to provide protection to the spinal cord.

The neural tube

The spinal cord and the spine form part of the neural tube. This develops very early in pregnancy - within the first 25 days after conception. The brain and the spinal tube develop from this neural tube. Spina bifida is caused by the failure of the tube to develop properly. Instead of the posterior (backward) protective arm being whole it is divided - that is, bifid. The fault may occur in one or more of the vertebrae but is most common around waist level.

Types of Spina Bifida

There are three main types of spina bifida:

Spina Bifida Occulta (hidden)

This is a very mild and common form and very rarely causes disability. There is usually a slight deficiency in the formation of one of the vertebrae. It can take the form of a dimple or small hair growth on the back. However, many people are unaware that they have spina bifida occulta as they display absolutely no symptoms of the condition.

How many people are affected?

Very many people have this condition. The vast majority of these will experience no symptoms or problems.

Spina bifida occulta may be detected by X-ray when investigations of back injury, for example, are being made. In such cases, it can be extremely frightening to be labelled as having spina bifida. It must be emphasised that it is of no consequence whatsoever for the vast majority of people having spina bifida occulta. Women with spina bifida occulta should ask their doctor to prescribe the higher dosage of folic acid when they plan to become pregnant - to help reduce the risk of their baby being affected by spina bifida.

Are there any complications?

Unfortunately, in some cases the cleft in the spine may cause problems. Sometimes the spinal cord may become tethered - that is, caught against the vertebrae. With growth, tension can cause inefficient functioning, affecting bladder control and mobility. If these symptoms are observed, it is very important to consult a GP who, if appropriate, can refer to a neurosurgeon.

Spina Bifida Cystica (cyst-like)

The visible signs are a sac or cyst, rather like a large blister on the back, covered by a thin layer of skin. There are two forms:

Meningocele In this form, the sac contains tissues which cover the spinal cord (meninges) and cerebro-spinal fluid. This fluid bathes and protects the brain and spinal cord. The nerves are not usually badly damaged and are able to function, therefore there is often little disability present. This is the least common form.

Myelomeningocele (meningomyelocele) This is the commoner of the two meningoceles and also the most serious. Here the sac or cyst not only contains tissue and cerebro-spinal fluid but also nerves and part of the spinal cord. The spinal cord is damaged or not properly developed. As a result, there is always some degree of paralysis and loss of sensation below the damaged vertebrae. The amount of disability depends very much on where the spina bifida is and the amount of nerve damage involved. Many children and adults with this condition experience problems with bowel and bladder control.

Cranium Bifida

Here the bones of the skull fail to develop properly. The sac which forms is known as encephalocele. It may contain tissue and cerebro-spinal fluid only. However, in some cases, part of the brain may also be present in the sac resulting in brain damage.

The most severe forms of cranium bifida are iniencephaly and anencephaly. Here, the brain does not develop properly or is absent, and the baby is either stillborn or dies shortly after birth.

Most babies born with spina bifida also have hydrocephalus (from the Greek hydro=water, cephalie=brain).