Manual of Surgery Volume I Part 38

#Clinical Features.#--The symptoms resulting from division and non-union of a nerve-trunk necessarily vary with the functions of the affected nerve. The following description refers to a mixed sensori-motor trunk, such as the median or radial (musculo-spiral) nerve.

_Sensory Phenomena._--Superficial touch is tested by means of a wisp of cotton wool stroked gently across the skin; the capacity of discriminating two points as separate, by a pair of blunt-pointed compa.s.ses; the sensation of pressure, by means of a pencil or other blunt object; of pain, by p.r.i.c.king or scratching with a needle; and of sensibility to heat and cold, by test-tubes containing water at different temperatures. While these tests are being carried out, the patient's eyes are screened off.

After division of a nerve containing sensory fibres, there is an area of absolute cutaneous insensibility to touch (anaesthesia), to pain (a.n.a.lgesia), and to all degrees of temperature--_loss of protopathic sensibility_; surrounded by an area in which there is loss of sensation to light touch, inability to recognise minor differences of temperature (72104 F.), and to appreciate as separate impressions the contact of the two points of a compa.s.s--_loss of epicritic sensibility_ (Head and Sherren) (Figs. 91, 92).

_Motor Phenomena._--There is immediate and complete loss of voluntary power in the muscles supplied by the divided nerve. The muscles rapidly waste, and within from three to five days, they cease to react to the faradic current. When tested with the galvanic current, it is found that a stronger current must be used to call forth contraction than in a healthy muscle, and the contraction appears first at the closing of the circuit when the anode is used as the testing electrode. The loss of excitability to the interrupted current, and the specific alteration in the type of contraction with the constant current, is known as the _reaction of degeneration_. After a few weeks all electric excitability is lost. The paralysed muscles undergo fatty degeneration, which attains its maximum three or four months after the division of the nerve.

Further changes may take place, and result in the transformation of the muscle into fibrous tissue, which by undergoing shortening may cause deformity known as _paralytic contracture_.

_Vaso-motor Phenomena._--In the majority of cases there is an initial rise in the temperature of the part (2 to 3 F.), with redness and increased vascularity. This is followed by a fall in the local temperature, which may amount to 8 or 10 F., the parts becoming pale and cold. Sometimes the hyperaemia resulting from vaso-motor paralysis is more persistent, and is a.s.sociated with swelling of the parts from dema--the so-called _angio-neurotic dema_. The vascularity varies with external influences, and in cold weather the parts present a bluish appearance.

_Trophic Phenomena._--Owing to the disappearance of the subcutaneous fat, the skin is smooth and thin, and may be abnormally dry. The hair is harsh, dry, and easily shed. The nails become brittle and furrowed, or thick and curved, and the ends of the fingers become club-shaped. Skin eruptions, especially in the form of blisters, occur, or there may be actual ulcers of the skin, especially in winter. In aggravated cases the tips of the fingers disappear from progressive ulceration, and in the sole of the foot a perforating ulcer may develop. Arthropathies are occasionally met with, the joints becoming the seat of a painless effusion or hydrops, which is followed by fibrous thickening of the capsular and other ligaments, and terminates in stiffness and fibrous ankylosis. In this way the fingers are seriously crippled and deformed.

#Treatment of Divided Nerves.#--The treatment consists in approximating the divided ends of the nerve and placing them under the most favourable conditions for repair, and this should be done at the earliest possible opportunity. (_Op. Surg._, pp. 45, 46.)

#Primary Suture.#--The reunion of a recently divided nerve is spoken of as primary suture, and for its success asepsis is essential. As the suturing of the ends of the nerve is extremely painful, an anaesthetic is required.

When the wound is healed and while waiting for the restoration of function, measures are employed to maintain the nutrition of the damaged nerve and of the parts supplied by it. The limb is exercised, ma.s.saged, and douched, and protected from cold and other injurious influences. The nutrition of the paralysed muscles is further improved by electricity.

The galvanic current is employed, using at first a mild current of not more than 5 milliamperes for about ten minutes, the current being made to flow downwards in the course of the nerve, with the positive electrode applied to the spine, and the negative over the affected nerve near its termination. It is an advantage to have a metronome in the circuit whereby the current is opened and closed automatically at intervals, so as to cause contraction of the muscles.

_The results_ of primary suture, when it has been performed under favourable conditions, are usually satisfactory. In a series of cases investigated by Head and Sherren, the period between the operation and the first return of sensation averaged 65 days. According to Purves Stewart protopathic sensation commences to appear in about six weeks and is completely restored in six months; electric sensation and motor power reappear together in about six months, and restoration is complete in a year. When sensation returns, the area of insensibility to pain steadily diminishes and disappears; sensibility to extremes of temperature appears soon after; and last of all, after a considerable interval, there is simultaneous return of appreciation of light touch, moderate degrees of temperature, and the points of a compa.s.s.

A clinical means of estimating how regeneration in a divided nerve is progressing has been described by Tinel. He found that a tingling sensation, similar to that experienced in the foot, when it is recovering from the "sleeping" condition induced by prolonged pressure on the sciatic nerve from sitting on a hard bench, can be elicited on percussing over _growing_ axis cylinders. Tapping over the proximal end of a _newly divided nerve_, _e.g._ the common peroneal behind the head of the fibula, produces no tingling, but when in about three weeks axis cylinders begin to grow in the proximal end-bulb, local tingling is induced by tapping there. The downward growth of the axis cylinders can be traced by tapping over the distal segment of the nerve, the tingling sensation being elicited as far down as the young axis cylinders have reached. When the regeneration of the axis cylinders is complete, tapping no longer causes tingling. It usually takes about one hundred days for this stage to be reached.

Tinel's sign is present before voluntary movement, muscular tone, or the normal electrical reactions reappear.

In cases of complete nerve paralysis that have not been operated upon, the tingling test is helpful in determining whether or not regeneration is taking place. Its detection may prevent an unnecessary operation being performed.

Primary suture should not be attempted so long as the wound shows signs of infection, as it is almost certain to end in failure. The ends should be sutured, however, as soon as the wound is aseptic or has healed.

#Secondary Suture.#--The term secondary suture is applied to the operation of st.i.tching the ends of the divided nerve after the wound has healed.

_Results of Secondary Suture._--When secondary suture has been performed under favourable conditions, the prognosis is good, but a longer time is required for restoration of function than after primary suture. Purves Stewart says protopathic sensation is sometimes observed much earlier than in primary suture, because partial regeneration of axis cylinders in the peripheral segment has already taken place. Sensation is recovered first, but it seldom returns before three or four months.

There then follows an improvement or disappearance of any trophic disturbances that may be present. Recovery of motion may be deferred for long periods--rather because of the changes in the muscles than from want of conductivity in the nerve--and if the muscles have undergone complete degeneration, it may never take place at all. While waiting for recovery, every effort should be made to maintain the nutrition of the damaged nerve, and of the parts which it supplies.

When suture is found to be impossible, recourse must be had to other methods, known as nerve bridging and nerve implantation.

#Incomplete Division of a Mixed Nerve.#--The effects of partial division of a mixed nerve vary according to the destination of the nerve bundles that have been interrupted. Within their area of distribution the paralysis is as complete as if the whole trunk had been cut across. The uninjured nerve-bundles continue to transmit impulses with the result that there is a _dissociated paralysis_ within the distribution of the affected nerve, some muscles continuing to act and to respond normally to electric stimulation, while others behave as if the whole nerve-trunk had been severed.

In addition to vasomotor and trophic changes, there is often severe pain of a burning kind (_causalgia_ or _thermalgia_) which comes on about a fortnight after the injury and causes intense and continuous suffering which may last for months. Paroxysms of pain may be excited by the slightest touch or by heat, and the patient usually learns for himself that the constant application of cold wet cloths allays the pain. The thermalgic area sweats profusely.

Operative treatment is indicated where there is no sign of improvement within three months, when recovery is arrested before complete restoration of function is attained, or when thermalgic pain is excessive.

#Subcutaneous Injuries of Nerves.#--Several varieties of subcutaneous injuries of nerves are met with. One of the best known is the compression paralysis of the nerves of the upper arm which results from sleeping with the arm resting on the back of a chair or the edge of a table--the so-called "drunkard's palsy"; and from the pressure of a crutch in the axilla--"crutch paralysis." In some of these injuries, notably "drunkard's palsy," the disability appears to be due not to damage of the nerve, but to overstretching of the extensors of the wrist and fingers (Jones). A similar form of paralysis is sometimes met with from the pressure of a tourniquet, from tight bandages or splints, from the pressure exerted by a dislocated bone or by excessive callus, and from hyper-extension of the arm during anaesthesia.

In all these forms there is impaired sensation, rarely amounting to anaesthesia, marked muscular wasting, and diminution or loss of voluntary motor power, while--and this is a point of great importance--the normal electrical reactions are preserved. There may also develop trophic changes such as blisters, superficial ulcers, and clubbing of the tips of the fingers. The prognosis is usually favourable, as recovery is the rule within from one to three months. If, however, neuritis supervenes, the electrical reactions are altered, the muscles degenerate, and recovery may be r.e.t.a.r.ded or may fail to take place.

Injuries which act abruptly or instantaneously are ill.u.s.trated in the crus.h.i.+ng of a nerve by the sudden displacement of a sharp-edged fragment of bone, as may occur in comminuted fractures of the humerus. The symptoms include perversion or loss of sensation, motor paralysis, and atrophy of muscles, which show the reaction of degeneration from the eighth day onwards. The presence of the reaction of degeneration influences both the prognosis and the treatment, for it implies a lesion which is probably incapable of spontaneous recovery, and which can only be remedied by operation.

The _treatment_ varies with the cause and nature of the lesion. When, for example, a displaced bone or a ma.s.s of callus is pressing upon the nerve, steps must be taken to relieve the pressure, by operation if necessary. When there is reason to believe that the nerve is severely crushed or torn across, it should be exposed by incision, and, after removal of the damaged ends, should be united by sutures. When it is impossible to make a definite diagnosis as to the state of the nerve, it is better to expose it by operation, and thus learn the exact state of affairs without delay; in the event of the nerve being torn, the ends should be united by sutures.

#Dislocation of Nerves.#--This injury, which resembles the dislocation of tendons from their grooves, is seldom met with except in the ulnar nerve at the elbow, and is described with injuries of that nerve.

DISEASES OF NERVES

#Traumatic Neuritis.#--This consists in an overgrowth of the connective-tissue framework of a nerve, which causes irritation and pressure upon the nerve fibres, sometimes resulting in their degeneration. It may originate in connection with a wound in the vicinity of a nerve, as, for example, when the brachial nerves are involved in scar tissue subsequent to an operation for clearing out the axilla for cancer; or in contusion and compression of a nerve--for example, by the pressure of the head of the humerus in a dislocation of the shoulder. Some weeks or months after the injury, the patient complains of increasing hyperaesthesia and of neuralgic pains in the course of the nerve. The nerve is very sensitive to pressure, and, if superficial, may be felt to be swollen. The a.s.sociated muscles are wasted and weak, and are subject to twitchings. There are also trophic disturbances. It is rare to have complete sensory and motor paralysis.

The disease is commonest in the nerves of the upper extremity, and the hand may become crippled and useless.

_Treatment._--Any const.i.tutional condition which predisposes to neuritis, such as gout, diabetes, or syphilis, must receive appropriate treatment. The symptoms may be relieved by rest and by soothing applications, such as belladonna, ichthyol, or menthol, by the use of hot-air and electric baths, and in obstinate cases by blistering or by the application of Corrigan's b.u.t.ton. When such treatment fails the nerve may be stretched, or, in the case of a purely sensory trunk, a portion may be excised. Local causes, such as involvement of the nerve in a scar or in adhesions, may afford indications for operative treatment.

#Multiple Peripheral Neuritis.#--Although this disease mainly comes under the cognizance of the physician, it may be attended with phenomena which call for surgical interference. In this country it is commonly due to alcoholism, but it may result from diabetes or from chronic poisoning with lead or a.r.s.enic, or from bacterial infections and intoxications such as occur in diphtheria, gonorrha, syphilis, leprosy, typhoid, influenza, beri-beri, and many other diseases.

It is, as a rule, widely distributed throughout the peripheral nerves, but the distribution frequently varies with the cause--the alcoholic form, for example, mainly affecting the legs, the diphtheritic form the soft palate and pharynx, and that a.s.sociated with lead poisoning the forearms. The essential lesion is a degeneration of the conducting fibres of the affected nerves, and the prominent symptoms are the result of this. In alcoholic neuritis there is great tenderness of the muscles.

When the legs are affected the patient may be unable to walk, and the toes may droop and the heel be drawn up, resulting in one variety of pes equino-varus. Pressure sores and perforating ulcer of the foot are the most important trophic phenomena.

Apart from the medical _treatment_, measures must be taken to prevent deformity, especially when the legs are affected. The bedclothes are supported by a cage, and the foot maintained at right angles to the leg by sand-bags or splints. When the disease is subsiding, the nutrition of the damaged nerves and muscles should be maintained by ma.s.sage, baths, pa.s.sive movements, and the use of the galvanic current. When deformity has been allowed to take place, operative measures may be required for its correction.

NEUROMA[5]

[5] We have followed the cla.s.sification adopted by Alexis Thomson in his work _On Neuroma, and Neuro-fibromatosis_ (Edinburgh: 1900).

Neuroma is a clinical term applied to all tumours, irrespective of their structure, which have their seat in nerves.

A tumour composed of newly formed nerve tissue is spoken of as a #true neuroma#; when ganglionic cells are present in addition to nerve fibres, the name _ganglionic neuroma_ is applied. These tumours are rare, and are chiefly met with in the main cords or abdominal plexuses of the sympathetic system of children or young adults. They are quite insensitive, and their removal is only called for if they cause pain or show signs of malignancy.

A #false neuroma# is an overgrowth of the sheath of a nerve. This overgrowth may result in the formation of a circ.u.mscribed tumour, or may take the form of a diffuse fibromatosis.

_The circ.u.mscribed or solitary tumour_ grows from the sheath of a nerve which is otherwise healthy, and it may be innocent or malignant.

_The innocent_ form is usually fibrous or myxomatous, and is definitely encapsulated. It may become cystic as a result of haemorrhage or of myxomatous degeneration. It grows very slowly, is usually elliptical in shape, and the solid form is rarely larger than a hazel-nut. The nerve fibres may be spread out all round the tumour, or may run only on one side of it. When subcutaneous and related to the smaller unnamed cutaneous nerves, it is known as a _painful subcutaneous nodule_ or _tubercle_. It is chiefly met with about the ankle, and most often in women. It is remarkably sensitive, even gentle handling causing intense pain, which usually radiates to the periphery of the nerve affected.

When related to a deeper, named nerve-trunk, it is known as a _trunk-neuroma_. It is usually less sensitive than the "subcutaneous nodule," and rarely gives rise to motor symptoms unless it involves the nerve roots where they pa.s.s through bony ca.n.a.ls.

A trunk-neuroma is recognised clinically by its position in the line of a nerve, by the fact that it is movable in the transverse axis of the nerve but not in its long axis, and by being unduly painful and sensitive.

[Ill.u.s.tration: FIG. 85.--Amputation Stump of Upper Arm, showing bulbous thickening of the ends of the nerves, embedded in scar tissue at the apex of the stamp.]

_Treatment._--If the tumour causes suffering it should be removed, preferably by sh.e.l.ling it out from the investing nerve sheath or capsule. In the subcutaneous nodule the nerve is rarely recognisable, and is usually sacrificed. When removal of the tumour is incomplete, a tube of radium should be inserted into the cavity, to prevent recurrence of the tumour in a malignant form.

_The malignant neuroma_ is a sarcoma growing from the sheath of a nerve.

It has the same characters and clinical features as the innocent variety, only it grows more rapidly, and by destroying the nerve fibres causes motor symptoms--jerkings followed by paralysis. The sarcoma tends to spread along the lymph s.p.a.ces in the long axis of the nerve, as well as to implicate the surrounding tissues, and it is liable to give rise to secondary growths. The malignant neuroma is met with chiefly in the sciatic and other large nerves of the limbs.

The _treatment_ is conducted on the same lines as sarcoma in other situations; the insertion of a tube of radium after removal of the tumour diminishes the tendency to recurrence; a portion of the nerve-trunk being sacrificed, means must be taken to bridge the gap. In inoperable cases it may be possible to relieve pain by excising a portion of the nerve above the tumour, or, when this is impracticable, by resecting the posterior nerve roots and their ganglia within the vertebral ca.n.a.l.

The so-called _amputation neuroma_ has already been referred to (p. 344).

_Diffuse or Generalised Neuro-Fibromatosis--Recklinghausen's Disease._--These terms are now used to include what were formerly known as "multiple neuromata," as well as certain other overgrowths related to nerves. The essential lesion is an overgrowth of the endoneural connective tissue throughout the nerves of both the cerebro-spinal and sympathetic systems. The nerves are diffusely and unequally thickened, so that small twigs may become enlarged to the size of the median, while at irregular intervals along their course the connective-tissue overgrowth is exaggerated so as to form tumour-like swellings similar to the trunk-neuroma already described. The tumours, which vary greatly in size and number--as many as a thousand have been counted in one case--are enclosed in a capsule derived from the perineurium. The fibromatosis may also affect the cranial nerves, the ganglia on the posterior nerve roots, the nerves within the vertebral ca.n.a.l, and the sympathetic nerves and ganglia, as well as the continuations of the motor nerves within the muscles. The nerve fibres, although mechanically displaced and dissociated by the overgrown endoneurium, undergo no structural change except when compressed in pa.s.sing through a bony ca.n.a.l.

The disease probably originates before birth, although it may not make its appearance till adolescence or even till adult life. It is sometimes met with in several members of one family. It is recognised clinically by the presence of multiple tumours in the course of the nerves, and sometimes by palpable enlargement of the superficial nerve-trunks (Fig. 86). The tumours resemble the solitary trunk-neuroma, are usually quite insensitive, and many of them are unknown to the patient. As a result of injury or other exciting cause, however, one or other tumour may increase in size and become extremely sensitive; the pain is then agonising; it is increased by handling, and interferes with sleep. In these conditions, a malignant transformation of the fibroma into sarcoma is to be suspected. Motor disturbances are exceptional, unless in the case of tumours within the vertebral ca.n.a.l, which press on the spinal medulla and cause paraplegia.