Neurological disorders

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11 Neurological disorders

CEREBRAL PALSY (Spastic paralysis: spastic paresis; Little’s disease)

The term cerebral palsy embraces a number of clinical disorders, mostly arising in childhood, the feature common to all of which is that the primary lesion is in the brain. The incidence of these disorders is such that cerebral palsy constitutes a major social and educational problem.

Cause. There is no single cause. Any event that results in damage to the brain may be responsible. Thus the causes may be classified into three groups: pre-natal, natal, and post-natal. Pre-natal causes include congenital defective development of the nervous system, and erythroblastosis leading to icterus gravis in the child, with consequent damage to the basal nuclei (kernicterus). Natal causes include damage to the brain and intracranial bleeds from birth injury, and anoxaemia with consequent cerebral anoxia. Prematurity is believed to be an important factor. Post-natal causes include infections such as pertussis, encephalitis, and meningitis, head injuries, and, in later life, cerebrovascular accidents (stroke). In children it is not always easy to ascribe the fault in a given case, but probably the commonest causes are damage to the brain during difficult labour and cerebral anoxia during birth.

Types. A number of clinical types may be recognised, of which the most important are:

1 spastic paresis
2 athetosis.

Mixed types also occur.

SPASTIC PARESIS

Pathology. Part of the motor cortex of the brain is replaced by areas of gliosis. There is degeneration of the pyramidal tracts.

Clinical features. Usually within the first year it is noticed that the child has difficulty in controlling the movements of the affected limbs, and there is delay in sitting up, standing and walking. Commonly the upper and lower limbs of one side are affected (hemiplegia). Less often there is involvement of a single limb (monoplegia), of both lower limbs (paraplegia), or of all four limbs (tetraplegia1). The trunk and face muscles may also be affected. On examination the features that are found constantly are weakness, spasticity, and imperfect voluntary control of movement. Usually there is also deformity, and in some cases there may be mental deficiency, impaired vision, or deafness. These various features are best considered separately.

Weakness. There is no true paralysis, but there may be fairly marked weakness of muscles. The weakness seldom affects all the muscles of a limb equally; often there is marked muscle imbalance which may lead to deformity.

Spasticity. The muscles are ‘stiff’: they resist passive movement of the joints, but when steady pressure is applied for some time they slowly relax, allowing the joint to be moved. When the pressure is released the spasm immediately returns. The tendon reflexes are exaggerated and muscle clonus may be elicited.

Lack of voluntary control. This is a striking feature, especially in severe cases. When the patient attempts to move a single group of muscles, other groups contract at the same time.

Deformity. When spasm and muscle imbalance are pronounced they lead eventually to the development of fixed deformity. The stronger muscles hold the limb constantly in an unnatural position, and secondary adaptive changes take place in the muscles and periarticular tissues. The commonest deformities in the upper limb are flexion contracture of the elbow, pronation deformity of the forearm, flexion of the wrist, and adduction of the thumb. In the lower limb the common deformities are adduction of the hip, flexion of the knee, and equinus of the ankle.

Mental deficiency. Impairment of mental capacity is sometimes present, but usually intelligence is normal. Lack of control of the facial and speech muscles may suggest mental impairment when in fact none exists. It is important that the medical advisers be not misled in this respect. Defective vision and deafness may also retard the child’s progress.

The severity of the disability varies widely from case to case. In the mildest examples the child is able to lead a normal active life with very little handicap, whereas in the worst cases the patient is almost helpless.

Prognosis. Since an essential part of the brain is destroyed and cannot be replaced, complete cure is impossible. All that can be hoped for is improvement. To achieve even this requires endless patience on the part of the patient and the attendants. Yet perseverance is nearly always well rewarded, and there are few cases in which worth-while improvement cannot be gained. Thus a patient formerly dependent upon others in many daily activities may often gain independence, and many who were previously unable to work become capable of earning their own living.

Treatment. Up to the age of about 5 years treatment may be carried out at non-residential centres, but after the age of 5 a child who is considerably disabled should be admitted to a special residential school where adequate facilities and trained staff are available.

The methods of treatment available are muscle training, corrective splinting, speech therapy, and operations on tendons, bones, or nerves.

Muscle training. This is an important part of the management of all except the mildest cases, and it is best carried out by a physiotherapist with experience of this very demanding work. The principles of muscle training are to teach the child to relax spastic muscles, to develop the use of individual muscle groups, and to improve coordination. Repetitive rhythmic movements are valuable. Stage by stage the child is instructed in dressing, toilet, feeding, and walking.

Corrective splinting. Splints or plasters are especially useful in overcoming the deformities induced by spastic muscles. Deformity is first corrected by gradual stretching of the contracted muscles, if necessary under anaesthesia. The limb is held by plaster in the over-corrected position for 6–8 weeks. Thereafter removable braces or splints (orthoses) may be used indefinitely to prevent recurrence of the deformity.

Speech therapy. Many spastic children have a speech defect which, with constant grimacing and salivation, may lead one to suppose that there is mental deficiency when in fact this is not so. In these cases the speech therapist is sometimes able to achieve a marked improvement.

Operative treatment. Operations for spastic paralysis should be approached with caution: striking benefit may be achieved in appropriate cases, but injudicious operation in unsuitable cases has often led to disappointing results. Operation may be upon tendon, joint, or nerve.

Tendon division or elongation. Division or lengthening of the tendon of a spastic muscle reduces its mechanical advantage and improves muscle balance. Examples are lengthening of the calcaneal tendon in a case of spastic equinus deformity, and tenotomy of the adductors of the hip for adduction deformity.

Tendon transfer. At certain sites transfer of the insertion of a muscle that is aggravating deformity may so modify the muscle’s action that it acts beneficially instead of as a deforming force. An example is the transfer of the insertion of the hamstring tendons from the tibia to the back of the femoral condyles in a case of flexion deformity of the knee: this eliminates the undesirable action of the spastic hamstrings in flexing the knee, while enhancing their desirable action as hip extensors.

Arthrodesis. When skeletal growth is complete it is sometimes of benefit to fuse a joint in a position of function, to eliminate persistent deformity from the pull of spastic muscles. Thus a wrist that lies constantly flexed may be fused in a neutral or slightly extended position, with consequent improvement in function.

Osteotomies. Division of the bone to correct angular and rotational deformities may be of value especially in the lower limb.

Neurectomy. The principle is to divide part or the whole of a nerve that supplies an overacting spastic muscle. An example is division of the anterior branch of the obturator nerve to overcome spastic adduction at the hip.

ATHETOSIS

Pathology. The main damage is in the basal nuclei.

Clinical features. The principal feature is the occurrence of generalised overlaid involuntary movements which have no pattern and which interfere with the performance of normal movements. Any part or the whole of the muscular system may be affected.

In mild cases the child is able to lead a fairly normal life, but in the worst examples the patient may be unable to sit up, walk, feed himself, or express himself in words, even though the mental state may be good.

Treatment. The first essential in treatment is to teach the child general relaxation. Once this has been achieved, purposeful voluntary movements can be taught. Splints and appliances may be required, but in pure athetosis there is no place for operations on the limbs. In some cases of severe athetosis improvement has been reported after surgical ablation of the globus pallidus.

SPINA BIFIDA

The term spina bifida implies a failure of the enfolding of the nerve elements within the spinal canal during early development of the embryo. The defect varies in degree and in its site (Fig. 11.1). In the mildest cases there is no more than a failure of fusion of one or more of the vertebral arches posteriorly, in the lumbo-sacral region. This is often of no clinical significance. Less often, the posterior bony deficiency is marked on the surface by an abnormality of the overlying skin, in the form of a dimple, a tuft of hair, a lipomatous mass, or a dermal sinus. In these cases there may be an underlying abnormality involving nerves of the cauda equina. These relatively minor varieties of spina bifida, in which the defect is not obvious at the skin surface, are termed spina bifida occulta. This contrasts with spina bifida aperta, in which there is a major defect of enfolding of the nerve elements, involving not only the bony vertebral arches but also the overlying soft tissues and skin, and often the meningeal membranes enclosing the spinal canal, so that the neutral tube itself is exposed and open. This major variant of spina bifida may occur anywhere in the spine but is commonest in the thoraco-lumbar region, and it is attended by grave impairment of nerve function.

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Fig. 11.1 Spina bifida. Diagrams showing four grades of severity of the posterior defect of the spinal canal. A Spina bifida occulta, B meningocele, C myelomeningocele, D rachischisis.

SPINA BIFIDA OCCULTA (Occult spinal dysraphism)

As noted above, the bony defect is simply a failure of fusion of the vertebral arches posteriorly (Fig. 11.1A). When there is neurological involvement the overlying skin nearly always shows an abnormality, as already described.

Impairment of nerve function may be caused in some such cases by tethering of the dura, and through this the spinal cord, to the skin surface by a fibrous membrane. Traction on the cord becomes gradually worse as the spinal column elongates disproportionately to the spinal cord: this can cause slow progression of the neurological deficit. A rather similar effect is caused by tethering of the distal end of the spinal cord by the filum terminale. Rarely, too, a bifid cord is transfixed by a delicate bar of bone crossing the spinal canal in the antero-posterior plane (diastematomyelia) with consequent tethering and progressive neurological impairment. In yet other cases the neurological fault may be a consequence of myelodysplasia, a congenital defect of development of nerve tissue.

In cases of occult spinal dysraphism there is no close correlation between the severity of the bony defect and the degree of neurological impairment. Often there is no neurological involvement; but on the other hand it may be severe. Clinically, the common manifestation of nerve involvement is muscle imbalance in the lower limbs, often with selective muscle wasting and deformity of the foot which often takes the form either of equino-varus or of cavus.

Investigation and treatment. The patient may be brought for advice because of an abnormality of the skin over the lumbo-sacral region, because of abnormality of the feet or perhaps just a limp, or because of urinary incontinence. A plain radiograph will show the extent of the bony deficiency.

If evidence of neurological impairment is lacking, treatment is not required. If neurological impairment or incontinence is present – and especially if there has been progressive deterioration – further investigations, including MR scanning and radiculography, are required. These may point to the presence of one of the structural lesions mentioned above, and in such a case neurosurgical intervention may be required: its object is to prevent further deterioration rather than to promote complete recovery.

SPINA BIFIDA APERTA (Overt spinal dysraphism; variations include rachischisis, myelomeningocele and meningocele)

The neurological deficit that complicates the more severe forms of spina bifida leads to varying degrees of motor, sensory, and visceral paralysis, and the consequent orthopaedic disability in the lower limbs may be complex. The number of children demanding orthopaedic care for such disabilities has increased in recent years because a far higher proportion of children born with myelomeningocele survived when the associated hydrocephalus was controlled by a ventriculo-cardiac or ventriculo-peritoneal shunt. Nevertheless the incidence is likely to fall dramatically since the advent of antenatal screening for alpha-fetoprotein, high-resolution ultrasound, and amniocentesis, with the option of termination of pregnancy in positive cases. It is also to be hoped that the incidence of spina bifida will be substantially reduced by the administration of folic acid to women before or at the commencement of pregnancy.

The cause is unknown: genetic factors may play a part but environmental factors are also probably involved. In particular, the influence of certain drugs – notably anti-epileptic drugs such as sodium valproate – has been recognised. Folic acid in a dosage of 5 mg daily taken before the commencement of pregnancy, or very early in pregnancy, offers some protection against the disorder.

Pathology. The basic structural defect – failure of total closure of the embryonal neural tube or of mesodermal tissue to invest it – varies in degree. In the most serious defect, rachischisis, the neural tube is open and exposed on the surface (Fig. 11.1D). Cerebrospinal fluid leaks from the exposed upper end of the central spinal canal. In myelomeningocele the neural tube is closed by a membrane but the skin covering is deficient. The spinal cord and the nerve roots are displaced posteriorly into the sac and are outside the line of the vertebral canal (Fig. 11.1C). In meningocele the bulging sac consists of meninges and fluid only, the nerve elements being normally situated (Fig. 11.1B). The skin may or may not be intact.

The distinction between closed lesions, with intact skin, and open lesions in which skin is deficient and nerve tissue is exposed on the surface of the body, is fundamental because open lesions may demand operation within a few hours of birth to close the defect, if indeed active intervention is deemed advisable.

The neurological lesion. Neurological deficit may be primary or secondary. Primary paralysis is present at birth and implies failure of development of part of the spinal cord (myelodysplasia). This varies widely in degree. In a fairly common example there may be normal innervation down to the level of the fourth lumbar segment and failure of development below that level. But the lesion may be either less extensive or more extensive than this.

Secondary paralysis develops after birth, either from drying or infection of exposed nerve tissue when closure of an open lesion has been delayed; from stretching of tethered nerve fibres as growth occurs; or from compression of nerve tissue within the abnormal spinal canal.

Clinical assessment. It is difficult in small infants to assess accurately the extent of motor and of sensory paralysis, and particularly to determine the state of bladder function. Nevertheless the important objective at the outset is to determine the level at which normal function of the spinal cord ceases. This is done by observing what movements the child makes, and correlating these with the root level. Sensibility can be determined by stimulating the skin lightly with a pin moved upwards from the limbs to the trunk until the child is awakened.

Motor paralysis. Motor paralysis affects mainly the lower limbs and to some extent the trunk. The extent of limb paralysis corresponds to the degree of dysplasia or of secondary damage in the spinal cord. It varies from the very mild, in which there may be no more than minor weakness of a single muscle group, to the very severe, in which there is total paralysis of the limbs. In the instance quoted above of normal cord function down to the fourth lumbar segment with loss of function below that, motor power is present only in the flexors and adductors of the hips, the quadriceps and the tibialis anterior: the remaining muscles are paralysed. This is a fairly common distribution but only one of an almost infinite variety. This uneven paralysis, with consequent muscle imbalance, leads commonly to secondary contractures with fixed deformity of hips, knees, or feet. It may also lead to dislocation of the hip, a common sequel to gluteal and abductor paralysis in the presence of strong flexors and adductors.

Sensory paralysis. Motor paralysis is nearly always accompanied by sensory paralysis of approximately the same distribution. This makes treatment more difficult because the use of corrective splints is hampered by the risk of pressure sores on the insensitive skin.

Visceral paralysis. Incontinence of bladder and bowel is present in a high proportion of patients.

Hydrocephalus. Associated hydrocephalus, usually due to the Arnold–Chiari malformation of the hind-brain, is common and was formerly largely responsible for the poor rate of survival among children with severe spina bifida.

Treatment. Every child with major neurological or visceral dysfunction from spina bifida should be admitted immediately to a special centre where a team of experienced specialists – including paediatrician, paediatric surgeon, neurosurgeon, and orthopaedic surgeon – may cooperate in deciding upon a programme that is best suited to the child. The team must first decide whether or not any surgical treatment, including closure of an open defect, is to be advised. This selective approach arose from review of large series where closure was universal: in the worst cases, with gross neurological deficit or hydrocephalus, the results were disastrous. In these it is probably better to adopt an expectant attitude, accepting the situation and relying simply on careful nursing and feeding. It has to be taken as inevitable that many of these badly affected infants will fail to survive.

The problems that are to be tackled when more active treatment is undertaken are often very complex. No firm rules can be laid down because there is so much variation between individual cases. It is sufficient here to indicate the main principles of orthopaedic treatment. These are:

1 to correct deformity
2 to maintain correction
3 to promote the best possible function in the affected.

In general, orthopaedic treatment should be deferred until the age of 1 to 3 years, to ensure that the child is thriving well and that the problems of hydrocephalus and renal function are satisfactorily controlled. This may have required a ventriculo-cardiac or ventriculo-peritoneal shunt to drain the excess cerebrospinal fluid, and urinary diversion to an artificial bladder for reasons of hygiene.

Correction of deformity. Deformity, whether of the hip, knee, or foot, should be corrected in the simplest way possible with the object of providing a limb that is straight, mobile, and with a plantigrade foot – that is, a limb that is best suited for weight bearing. This may be achieved by a combination of splintage and surgical treatment, depending on the level of paralysis and the joints affected. Splints and plasters are useful for controlling flail joints and for maintaining correction after operative procedures, but they must be fitted and used with care because of the risk of pressure sores involving the insensitive skin. When fixed deformity is present as a result of unbalanced or spastic muscle action operation is needed to divide or elongate tight structures – tendon, muscle, ligament, or joint capsule – in order to achieve a neutral anatomical position. Paralytic dislocation of the hip is common and may necessitate posterior transfer of the iliopsoas muscle to the greater trochanter (to act as a hip abductor), sometimes combined with femoral or pelvic osteotomy, to maintain stability. In the more severe lesions, where wheelchair locomotion is inevitable, it may be better to leave the dislocation unreduced while preserving mobile hips. Spinal deformity, often a combination of kyphosis and scoliosis, may require surgical correction and fusion, but the complications of pseudarthrosis and pressure sores are common.

Development of limb function. Even when lower limb paralysis is severe it is often possible to get the child walking with crutches once deformities have been overcome. In many cases external bracing in the form of limb calipers or swivel walkers is also required, and prolonged training by a skilled physiotherapist is essential if maximal function is to be achieved.

POLIOMYELITIS (Anterior poliomyelitis; infantile paralysis)

Poliomyelitis is a virus infection of nerve cells in the anterior grey matter of the spinal cord, leading in many cases to temporary or permanent paralysis of the muscles that they activate. In many countries the incidence of the disease increased so much in the years succeeding the Second World War that its management – or rather the management of the paralytic disabilities that it produces – became one of the foremost problems of orthopaedic surgery. However, in the 1950s the incidence decreased very markedly in Western countries, in consequence of nationwide programmes of prophylactic vaccination; so much so that the disease has now been virtually eliminated. Nevertheless it is still encountered in certain countries of Asia and Africa.

Cause. It is caused by infection with a virus, of which at least three types have been identified.

Pathology. After gaining access to the body through the nasopharynx or the gastro-intestinal tract, the virus finds its way to anterior horn cells of the spinal cord (Fig. 11.2) and sometimes to nerve cells in the brain stem. According to the virulence of the infection the cells may escape serious harm, or they may be damaged or killed. If cells are damaged there is paralysis of the corresponding muscles but recovery is possible; if the cells are killed paralysis is permanent. The extent and distribution of the lesions vary widely from case to case.

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Fig. 11.2 Section of spinal cord. The virus of poliomyelitis attacks the anterior horn cells. If the cells are killed there is permanent paralysis of the corresponding muscle fibres. If the cells are damaged but not killed the paralysis is recoverable.

Clinical features. Although it is still commonest in children, poliomyelitis often attacks young adults. For descriptive purposes the disease is conveniently divided into five stages.

Stage of incubation. This is the interval between infection and onset of symptoms. It is thought to be about 2 weeks. There are no symptoms.

Stage of onset. This lasts about 2 days. The symptoms are like those of influenza: headache, pains in the back and limbs, and general malaise. Examination may show mild pyrexia, often with neck rigidity if flexion is attempted, and tenderness of muscles. Lumbar puncture may show an increase of round cells in the cerebrospinal fluid. In many cases the disease does not progress beyond this stage, the patient making a rapid and complete recovery.

Stage of greatest paralysis. This stage, when it occurs, lasts about 2 months. Paralysis develops rapidly and is usually at its greatest within a few hours, thereafter remaining unchanged throughout this stage. The extent and distribution of the paralysis vary enormously. There may be no paralysis at all, or it may be total. In this stage muscle pain continues, and unparalysed muscles are often painful if stretched. If the respiratory muscles are paralysed preservation of life will be dependent upon the use of a ventilator.

Stage of recovery. When any recovery of power occurs it may continue for about 2 years.1 The degree of recovery varies within the widest limits. There may be complete recovery or there may be none.

Stage of residual paralysis. Paralysis or weakness persisting after two years is permanent. Its degree and extent vary from insignificant local weakness to almost total paralysis of the trunk and all four limbs. Weakness or paralysis is accompanied by obvious wasting of the affected muscles. This in turn is associated with defective growth of the bones and consequent shortening if the disease occurs in childhood.

Prognosis. In round figures, it may be stated that half of all patients clinically infected with poliomyelitis have no paralysis at any time. Of those with paralysis, 10% die (usually from respiratory paralysis); 30% recover fully; 30% have moderate permanent paralysis; and 30% have severe permanent paralysis.

Prophylaxis. In Britain prophylactic vaccination is by an attenuated living virus, taken by mouth.

Treatment. No specific treatment is available. In few diseases is the doctor so powerless to influence recovery: the patient either will or will not recover his muscle power, depending upon the severity of the neurological damage; and there is very little that the doctor can do about it. The main duties of the orthopaedic team are to prevent deformity, to assist returning muscle power by graduated exercises, and to reduce residual disability in the final stage by the provision of appropriate appliances or by operations on joints or muscles. The treatment appropriate to each stage of the disease is best considered separately.

Stage of onset. The patient should rest in bed and may be given sedatives as required.

Stage of greatest paralysis. In this stage artificial respiration by a ventilator may be necessary to preserve life if the respiratory muscles are paralysed. Paralysed limbs may have to be supported by splints in a neutral position to prevent the development of contractures with consequent deformity. Fixed equinus deformity of the ankle and foot is particularly liable to develop in cases of paralysis of the anterior leg muscles unless the foot is maintained at a right angle to the leg. Joints should be put through a full range of movement daily, so far as pain allows. Muscle pain may be eased by warmth, as from hot packs. Whether or not the patient must remain in bed in this stage will depend upon the degree and distribution of the paralysis.

Stage of recovery. The patient should be under the close supervision of a skilled physiotherapist. Any muscle that is seen to be regaining power must be exercised, gently and patiently at first, but later very strenuously, to encourage the greatest possible redevelopment. It should be remembered that power may improve partly as a result of recovery of the damaged nerve cells, but partly also from hypertrophy of muscle fibres that have escaped paralysis. When possible, walking should be resumed at this stage, if necessary with the aid of appliances, crutches, or sticks.

Stage of residual paralysis. The disability in this stage can often be reduced either by the provision of suitable external appliances (orthoses), or by operation.

Appliances (orthoses). The purpose of external appliances or orthoses is to support joints that are no longer adequately controlled by muscles. They are required more often for the lower limbs and spine than for the upper limbs. The following are commonly prescribed:

1 spinal brace, to support a weakened spine
2 abdominal support, to check abdominal protrusion when the abdominal muscles are weak
3 knee caliper (Fig. 11.3), to hold the knee extended in cases of severe quadriceps paralysis
4 below-knee brace to stabilise a flail ankle or foot (Fig. 11.4)
5 ankle foot orthosis (Fig. 11.5), to hold the foot up when the dorsiflexor muscles are paralysed.
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Fig. 11.3 A Articulated knee ankle foot orthosis (KAFO) with locking joints to control an unstable knee and ankle joint. B Patient wearing knee ankle foot orthosis.

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Fig. 11.4 A Moulded polythene ankle foot orthosis (AFO) to control ankle instability. B Patient wearing ankle foot orthosis.

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Fig. 11.5 A Moulded polythene orthosis to control drop foot. B Patient wearing drop foot splint which is worn inside a shoe.

Operative treatment. Two main groups of operations are available:

1 arthrodesis of joints
2 muscle or tendon transfers.

Arthrodesis is a valuable method of stabilising joints that have lost their controlling muscles. It is particularly applicable to the shoulder, elbow, wrist, spine, ankle, and foot.

In muscle or tendon transfer operations the object is to use a healthy muscle to replace the function of one that is paralysed. The method finds its chief application in the upper limb. Examples are the transfer of part of the pectoralis major muscle to replace the function of paralysed elbow flexors, transfer of wrist flexors to serve as extensors of the fingers, and transfer of a flexor digitorum superficialis tendon to replace a paralysed opponens muscle.

PERIPHERAL NERVE LESIONS

Disorders of the peripheral nerves come largely within the sphere of the neurologist, but the orthopaedic surgeon is concerned with lesions that have a mechanical basis and with those that lend themselves to reconstructive surgery.

Pathology. Nerves may be damaged by laceration, contusion, traction, compression, friction, burns, or ischaemia. According to its severity, a nerve lesion may be classified as neurapraxia, axonotmesis, or neurotmesis. In neurapraxia the damage is slight and it causes only a transient physiological block. Recovery occurs spontaneously within days or weeks. In axonotmesis the internal architecture of the nerve is preserved, but the axons are so badly damaged that peripheral degeneration occurs. Recovery can occur spontaneously, but it depends upon regeneration of the axons and may take many months (1 mm/day is the usual speed of regeneration). In neurotmesis the structure of the nerve is destroyed by actual division or by severe scarring. Recovery is possible only after excision of the damaged section and end-to-end suture of the stumps, or after nerve grafting.

Clinical features. The effects of complete loss of conductivity of a nerve are motor, sensory, and autonomic. They are localised to the distribution of the nerve affected. Motor changes: The muscles are paralysed and wasted. Changes occur in the electrical reactions, but they take between two and three weeks to develop. These changes were described on page 27. Sensory changes: There is loss of cutaneous, deep, and postural sensibility. Autonomic changes: These include loss of sweating, loss of pilomotor response to cold (‘goose-skin’), and temporary vasodilation with increased warmth, which, however, is followed later by vasoconstriction and coldness.

Complications. Injury to a peripheral nerve trunk is occasionally followed by severe burning pain in the distribution of the nerve. This is termed causalgia. It is a complication of incomplete rather than of complete lesions, and with few exceptions it is confined in the upper limb to the brachial plexus or the median nerve, and in the lower limb to the sciatic nerve or the tibial nerve. Relentless pain makes this a very disabling complication, the only effective treatment of which is by sympathetic denervation of the limb.

Treatment. Open injuries. If a nerve is believed to have been divided – for example, by a penetrating injury – the wound should be explored and the nerve identified. If the nerve is severed the ends should be examined carefully to determine the extent to which they have been damaged by laceration or bruising. Only in the case of a clean-cut division with minimal damage to the severed ends should primary suture be carried out. If these criteria are not satisfied it is better simply to tack the ends together with one or two sutures and to delay definitive repair – preferably with a magnification technique – until 2 or 3 weeks after the injury. At that time the extent of the scarring, and consequently the length of nerve to be resected, can be determined accurately, and thickening of the nerve sheath makes suture technically easier.

Closed injuries. In closed injuries complicated by nerve paralysis it is usually assumed that the nerve is in continuity, and expectant treatment is adopted at first. If signs of recovery are not observed within the expected time (calculated from the site of injury and length to be regenerated) exploration is advised. Evidence of muscle re-innervation may be derived from electromyography at an earlier stage than from clinical examination. Such exploration should seldom be delayed for more than 3 or 4 months, because long delay prejudices successful repair if the nerve has been divided.

When a nerve lesion has been caused by stretching, compression, or ischaemia the essential principle of treatment is to ensure that the harmful conditions are relieved, if necessary by operation to free the nerve or to remove a compressing agent.

Nerve grafting. When the gap to be bridged between healthy neurones proximally and distally is large, nerve grafting is preferable to attempted direct suture under tension. A thick nerve may be bridged by multiple grafts from a thinner nerve – for example the sural nerve. By microsurgical techniques it is also now possible to transfer a nerve complete with its blood supply, to bridge a major defect. Freeze-thawed muscle grafts have been used experimentally as an alternative to nerve grafts. They may provide a chemotactic stimulus for nerve regeneration as well as providing a microskeleton to guide axonal fibres across the gap, which should not exceed 3 cm.

BRACHIAL PLEXUS INJURIES

Injuries of the brachial plexus are a major cause of partial or complete loss of function of the upper limb. Most of such injuries are caused by forcible distraction of the upper extremity away from the neck by violent depression of the shoulder. The main injury is sustained by the upper roots of the plexus, which may be stretched, torn, or even avulsed from the spinal cord. There is consequent paralysis of the muscles supplied through the upper roots – chiefly the abductor and lateral rotator muscles of the shoulder and the flexors of the elbow (Erb type of paralysis). A less common type of brachial plexus injury is caused by forcible elevation of the arm and shoulder. This tends to drag on the lower roots of the plexus, with consequent motor and sensory paralysis mainly in the forearm and hand (Klumpke type of paralysis). In the most severe injuries the whole plexus is torn or avulsed and there is total paralysis of the upper limb.

Brachial plexus lesions in infants

In infants, brachial plexus injuries are usually caused during delivery (obstetrical palsy), and the risk is greatest in difficult breech deliveries. The upper arm type (Erb’s palsy) is the more common. Soon after birth it is noticed that the child does not move the arm as he normally should. Unopposed action of the unparalysed muscles tends to bring the arm into a position of adduction and medial rotation, and secondary contracture of the soft tissues may lead to fixed deformity in that position.

Prognosis depends upon the severity of the stretching injury. If this was mild full recovery may occur, though it may take many months; but in a severe case there may be permanent loss of power and sensibility. The prognosis is less favourable in the rare lower arm type of lesion (Klumpke type) than in the commoner upper arm type.

Treatment. In a mild case the mother should be taught to move the limb frequently through the full range, to prevent fixed contracture. In a severe case seen early it may be possible, if the requisite expertise is available, to restore continuity of the damaged nerves by early operation. In late cases with permanent paralysis and deformity there is a place for late reconstructive operations such as corrective (rotation) osteotomy of the humerus, arthrodesis of the shoulder or tendon transfer operations.

Brachial plexus lesions in adults

In adults brachial plexus injuries are usually caused by forcible depression of the shoulder. By far the commonest cause is a motorcycling accident.

It is important to distinguish between preganglionic lesions, in which the nerve roots are avulsed from the spinal cord, and postganglionic lesions, in which the nerves are torn more distally. Preganglionic lesions are irrecoverable, whereas there is potential for some recovery in postganglionic lesions. Clinical and electrical tests may indicate the approximate site of the lesion, but special investigations are needed for more accurate assessment. Initially, spinal root imaging by radiculography may show dural pouches at the sites of nerve avulsion. CT scanning with contrast gives the best information on the extent of the damage and is superior to MRI scanning. In the last resort surgical exploration may be needed to localise the lesion definitively, especially in the first few days after injury when the prospect of successful repair is most favourable. The measurement of intra-operative nerve action potentials is valuable: when these are present distal to the lesion a substantial number of large fibres have survived the injury, so excision and grafting are unnecessary.

Treatment. For irrecoverable (preganglionic) lesions all that can be done is to make the best use of any function that remains. Tendon or muscle transfers, to replace the action of paralysed muscles, may be appropriate in selected cases, and arthrodesis of the shoulder may sometimes be indicated if strong scapular muscles and useful hand function are preserved.

If, however, it is confirmed at operation that the roots have been torn across rather than avulsed, repair by nerve grafting may be attempted with some hope of success. Nerve transfers that have been used include: redirection of the accessory nerve to the suprascapular nerve to improve shoulder function; and transfer of the third or fourth intercostal nerve to the musculocutaneous nerve to restore elbow flexion. Even limited recovery is well worth-while, and may reduce the level of severe causalgic pain; nevertheless the outlook for good recovery of motor and sensory function is always very doubtful, especially in the forearm and hand, and severe permanent disability is usually to be expected.

1 Also termed (though less correctly because Latin is mixed with Greek) diplegia or quadriplegia.

1 It will be observed that the figure 2 appears in the stated duration of each of the first four stages – 2 weeks, 2 days, 2 months, 2 years. These are only very approximate figures, but they are easily memorised.

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