The Child with Spina Bifida

Elizabeth M. Anderson, Bernie Spain

• Publisher: Routledge
• Year: 2016
• ISBN:
  9781317326328
• Edition: 1
• Topic: Sciences sociales
• Subtopic: Handicaps en sociologie

First published in 1977, this book focuses on the disability of spina bifida in children. Children with the condition frequently suffer with severe physical handicaps such as lower limb paralysis and incontinence, as well as intellectual impairment. It can be difficult for the families of these multiply handicapped children and they often require the help of professionals from many disciplines. In this book, the authors focus on practical suggestions for alleviating many of the problems brought about by the condition. Their suggestions are designed to help parents, as well as professionals.

1 Medical aspects

1 Physical and medical problems

DOI: 10.4324/9781315656861-2

Introduction

The term spina bifida refers, strictly speaking, to a developmental defect of the spinal column in which the arches of one or more of the spinal vertebrae have failed to fuse together so that the spine is ‘bifid’, a Latin term meaning split in two. Through this gap in the spine either the spinal cord itself or its surrounding membranes protrude, depending upon which of several types of spina bifida the child is suffering from. A great deal of publicity has been given to this condition during the last decade and most people to whom the term means anything at all probably associate it with a severely disabled child with paralysed legs and incontinence of the bladder and bowel. It is important to point out from the start that the general term ‘spina bifida’ embraces a group of developmental defects of the spinal column ranging from a condition called spina bifida occulta which is very common but usually has no effect on function, to the far more complex and serious condition which the term ‘spina bifida’ has come to mean to most of the public, i.e. myelomeningocele. (Medical terms summarized in Glossary, p. 313.)

How the condition develops

In the normally developing human embryo the central nervous system, including the brain and the spinal cord, begins as a single sheet of cells: this sheet of cells develops during the second week of pregnancy into what is called the neural plate (Fig. 1.1a). During the third week of pregnancy the neural plate enlarges and forms a symmetric longitudinal groove (Fig. 1.1b). In the fourth week the neural groove deepens and folds develop on either side, which eventually fuse so that instead of an open groove a closed tube is formed (Fig. 1.1c and d). This elongated hollow cylinder is called the neural tube and it eventually differentiates into the brain and the spinal cord. Following this, supportive and protective tissues develop to enclose the spinal cord and the brain (for example, the meninges), and finally a bony covering is formed, the vertebrae of the spinal column (which enclose and protect the spinal cord) and the cranium (the skull).

Figure 1.1 Diagram of transverse section of embryos at different ages to show development of the spinal cord.

In spina bifida or any other neural tube defect, some part of the nerve cord fails to close or fuse and the nerve cord at that point remains immature and improperly formed. If the nerve cord has failed to form properly then the supporting tissues, including the vertebrae or the cranium, will also be abnormal.

From the cavities within the brain (the ventricles), around which the nerve tissue is folded, a fluid is produced called cerebro-spinal fluid (CSF) which bathes and protects the nerves cells. In the normally developing foetus, the CSF circulates freely, flowing down into the spinal column through a small hole in the base of the skull, the foramen magnum, through which the spinal nerves ascend and descend from the brain (see Fig. 1.6, p. 32). Commonly associated with spina bifida is a second abnormality found at the base of the brain, called the Arnold-Chiari malformation. This is a herniation (protrusion) of the lower brain downwards through the foramen magnum and a general disarrangement of the lower brain structures. When this abnormality occurs it is usually accompanied by hydrocephalus, that is, a build-up of CSF within the brain, due to an obstruction in the normal circulation of the fluid. If the build-up of CSF is not checked, it causes the nerve cells to become stretched and crushed, and stretches the infant skull so that it enlarges to accommodate the additional fluid.

Interference with the normal growth and development of the neural tube and in particular with the closure of the neural tube during the early weeks of pregnancy may result in any of the disorders described in this chapter. The reasons for this interference with normal development appear to be very complex and are not yet fully understood: probably both genetic and a variety of environmental factors are involved, and these are discussed more fully in chapter 2. The exact nature of the neural tube disorder, however, will depend both upon which part of the neural tube fails to develop normally and on the extent of the interference with normal growth. If there is a failure of closure in the midline or lower end of the neural tube, then spina bifida will result. If the failure is at the upper end, the head end of the tube, this will result in either cranium bifidum or anencephaly.

Spina bifida

Much of the terminology used about spina bifida is still confusing. However, the classification used by Smith (1965) is the generally accepted one, the two main divisions being into (a) spina bifida occulta and (b) spina bifida cystica, this being subdivided into two main conditions, (i) meningocele and (ii) myelomeningocele.

In spina bifida occulta (Latin=hidden) the vertebral arches do not fuse: there is not, however, any distension of the meninges and the spinal cord and its membranes are generally (although not always) normal. The site of the spinal defect is sometimes marked by a slight swelling, a dimple in the skin, or a tuft of hairs but there is often no external evidence of the defect. This condition is very common and rarely has any consequences on function.

The other main type of spina bifida, spina bifida aperta (Latin= open) or cystica (cyst-like) is a condition in which some of the spinal cord tissue herniates into a sac-like cyst filled with cerebro-spinal fluid. There are two major sub-types of spina bifida cystica, meningocele (Fig. 1.2b) and myelomeningocele (Fig. 1.2c).

Figure 1.2 Diagram showing section through normal spine (a) meningocele (b) and myelomeningocele (c) (Adapted from Benda, C. E. Developmental Disorders of Mentation and Cerebral Palsies, 1952, courtesy of Grune and Stratton, Inc., New York).

Spina bifida meningocele is the less serious and the less common type, affecting between approximately 15 per cent and 25 per cent of all children with spina bifida cystica. In this type (Fig. 1.2b) the meninges bulge through the gap in the spine to form a smooth cystic sac usually covered by normal skin. This sac usually contains only meninges and cerebro-spinal fluid. The nerve cord functions normally, however, so that in cases of spina bifida meningocele there will be no significant degree of impairment.

The other major type is myelomeningocele (Fig. 1.2c). Again, there is failure of the vertebrae to fuse and distension of the meninges, but this condition differs from meningocele in that the spinal cord not only protrudes into the sac but is itself abnormal, the result being permanent and irreversible neurological disability. Within this type of spina bifida many variations in the structure of the spinal cord are found and different terms are used to describe these.

The changes in the spinal cord are not confined to the level of the main mass of the lesion; if any cord does continue below the level of the lesion it is usually abnormal. Again, above the main mass the cord is also frequently abnormal for several spinal segments, and indeed autonomic abnormalities may occur at any point in the upper spine (Emery and Lendon, 1973).

Cranium bifidum and anencephaly

The other major neural tube defects occur when there is a failure to fuse at the head end of the nerve cord. The term cranium bifidum refers to a defect in the fusion of the bones of the skull (cranium), usually at the back of the head, which allows soft tissues to herniate. Some of the lesions contain only meninges and some actual brain tissue but the term encephalocele is commonly applied to the various lesions associated with cranium bifidum. Encephaloceles may be quite small and covered with skin in which case the outlook is good: often, however, the swelling is large and only covered by a thin membrane and here the outlook is very poor.

In anencephaly there is an actual defect of development of the entire anterior part of the brain, not simply a cranial defect, with a failure of the formation of the vertex of the skull and incomplete formation and degeneration of the cerebral lobes of the brain; the basal parts of the brain then lie exposed on the surface (Carter, 1969). Anencephalics are commonly stillborn and those born alive do not survive.

Clinical aspects of spina bifida myelomeningocele

When the baby is born the spinal defect, whether it is a meningocele (containing only cerebro-spinal fluid and the meninges) or a myelomeningocele (containing also the spinal cord tissue) may have a variety of appearances. Most commonly there is a raised swelling or ‘sac’ which may be located at any point along the spinal column, and which varies greatly in size, extent and contents (Plate 1).

It looks rather like a large blister on the surface of the back through which can be seen the cerebro-spinal fluid, and, in myelomeningocele, the abnormal or primitive nerve cord can also be seen, often adhering to the tissue covering the sac. The sac may be covered by normal skin. Most commonly it is covered by a very flimsy membrane, the arachnoid, at the centre of the defect, with normal skin towards the outer edges.

Because the skin covering the lesion is defective, the area is exposed to injury and infection, the greatest danger being the development of meningitis. In addition, if the cystic sac is allowed to expand there may be stretching of the nerve roots leading to an increase in the paralysis and weakness of the legs or abdominal muscles. If the lesion is not protected, the exposed nerves may dry out and further deteriorate.

Consequently it has been common practise in this country since the early 1960s to ‘repair’ the spinal lesion by covering it with skin flaps where possible within twenty-four hours of birth. In this operation the spinal cord is put into its normal place within the spinal cavity and is covered with skin and other tissues to save the exposed tissue from infection and other damage and to reduce the risk of meningitis. However, if the lesion is a very bad one and little movement has been preserved, it may not be necessary to operate immediately, provided that effective measures can be taken to prevent infection or further damage to the nerve cord.

Locomotor and associated problems

The extent of lower limb paralysis depends on where the spinal lesion is, its severity and its extent, the location of the main areas of the vertebral column (spine) being shown in Fig. 1.3 below.

Figure 1.3 The vertebral column. The vertebral column consists of thirty-three vertebrae, a series of bony rings forming a hollow canal enclosing and protecting the spinal cord. Thirty-one pairs of spinal nerves originate from the cord. The main parts of the trunk and limbs with which the spinal nerves connect are indicated above together with the main internal organs controlled by the autonomic nerves which connect with particular sections of the spinal cord.

In general lumbar and in particular thoraco-lumbar lesions are likely to produce quite severe paralysis. Survivors with cervical lesions, which are usually simple meningoceles, are rarely handicapped. Sacral lesions also result in a slight handicap, because fewer nerve roots are implicated.

Broadly speaking the child will be unable to move those muscles which receive their nerve supply from the spinal cord below the level of the lesion, although surviving children with lesions at the upper thoracic and cervical levels (rather a small proportion of all children with myelomeningoceles), are usually free from severe locomotor disabilities. The majority of children with myelomeningocele have lesions at lower levels than this, particularly in the lumbar and lumbo-sacral regions since this area of the spinal cord is the last part of the neural tube to close. Smith (1965) suggests that four main groups can be distinguished. Most severely handicapped are those children with lesions at or above the third lumbar vertebra who are totally paraplegic and will need total support to the lower limbs. The next group, with lesions at or below the fourth lumbar vertebra, will have suffered from paralysis of some (but not all) of the muscles of the hips and knees, as well as paralysis of the feet and will need support in these areas. A third group with lesions at the first and second sacral vertebrae may have just adequate function left in the hips, but the feet will need support. Least handicapped are children with lesions at or below the third sacral vertebra: their lower limb function will be normal, but they may be incontinent.

Overall, between a third and a half of children with myelomeningocele are left with a total flaccid paraplegia while most of the others will have significant locomotor problems (Gabriel, 1974). Whatever the degree of lower limb paralysis, hydrocephalus makes independent walking more difficult as it dist...