Spina Bifida literally means ‘split spine’
Spina Bifida is a relatively common condition, which affects about one in every 1000 children born per year in Ireland. Ireland has one of the highest incidences of Spina Bifida births in the world. Spina Bifida is the most common neural tube defect (NTD) which causes incomplete development of the spinal cord. Translated, it literally means ‘split spine’.
The Central Nervous System (CNS)
The nervous system is essentially a biological information highway, and is responsible for controlling all the biological processes and movement in the body, At the centre of this system is the Central Nervous System (CNS).
The CNS consists of the brain and spinal cord. It is responsible for receiving and interpreting messages and also sends out messages, either consciously or unconsciously.
The spine is made up of separate bones called vertebrae, which normally cover and protect the spinal cord. With Spina Bifida, some of these vertebrae are not completely formed. Instead, they are split and the spinal cord and its coverings usually protrude through a sac-like bulge on the back, covered with a thin membrane.
The Neural Tube
In the developing vertebrate, the neural tube is the embryo’s precursor to the central nervous system.
The central nervous system and spine develops between the 14th and 23rd day after conception. Spina bifida occurs when the neural tube fails to close correctly. The vertebrae also fail to close in complete rings around the affected portion of the spinal cord. This leaves a gap posteriorly (at the back), involving one or more vertebrae. Spina Bifida may occur in one or more of the vertebrae but it is most common around waist-level.
Types of Spina Bifida
Spina Bifida Occulta
This is known by some people as ‘hidden’ Spina Bifida and is very common. The split in the bone of the spine is small and the spinal cord and main nerves cannot bulge out and so little or no damage is done. The only thing to see on the back may be a dimple, tuft of hair, or a red mark. Someone with Spina Bifida Occulta may not have any problems at all and probably wouldn’t know they had this condition unless an x-ray of the back was taken. Antenatal tests usually do not detect this type of Spina Bifida, before birth.
In this type of Spina Bifida, the split in the bones is not big enough for the spinal cord to come through, but a ‘balloon’ of skin filled with fluid and blood vessels bulges out. This fluid which comes from around the spinal column is called cerebro-spinal fluid (CSF). Usually the nerve supply is not affected. The degree of disability is usually less severe than Myelomeningocele, but can only be determined as the child develops.
This is the most common form of Spina Bifida. The areas effected are dependent on the location of the split. The split contains the spinal cord and nerves are held in the sack which will also be filled with fluid. The spinal cord and nerves become exposed and the degree of damage will determine the extent of disability. A Myelomeningocele is most frequently found in the lumbar area, but can occur anywhere along the spine.
In the minority of cases of NTD’s, the split is high up and involves the back of the head (skull). There is a balloon-like swelling but this does not contain important nerves of the spinal column. Some Encephaloceles are small, covered with skin and the children usually grow up without major implications. Sometimes, however, it is large and may contain some of the brain and this can severely affect the baby’s eyesight and can cause learning disabilities. Sometimes, however, they can contain large volumes of brain tissue, so that the reaming brain is small, poorly developed and severely Hydrocephalic.
Anencephaly results in only minimal development of the brain. Often, the brain lacks part or all of the cerebrum (the area of the brain that is responsible for thinking, vision, hearing, touch, and movement). Due to the extent of under-development of the brain babies affected by this condition are unlikely to survive outside the uterus, may be stillborn or die shortly after birth. Treatment is supportive.