THE NERVES
Anatomy--INJURIES OF NERVES: Changes in nerves after division;
Repair and its modifications; Clinical features; _Primary and
secondary suture_--SUBCUTANEOUS INJURIES OF
NERVES--DISEASES: _Neuritis_; _Tumours_--Surgery of
the individual nerves: _Brachial neuralgia_; _Sciatica_;
_Trigeminal neuralgia_.
#Anatomy.#--A nerve-trunk is made up of a variable number of bundles of
nerve fibres surrounded and supported by a framework of connective
tissue. The nerve fibres are chiefly of the medullated type, and they
run without interruption from a nerve cell or _neuron_ in the brain or
spinal medulla to their peripheral terminations in muscle, skin, and
secretory glands.
Each nerve fibre consists of a number of nerve fibrils collected into a
central bundle--the axis cylinder--which is surrounded by an envelope,
the neurolemma or sheath of Schwann. Between the neurolemma and the axis
cylinder is the medullated sheath, composed of a fatty substance known
as myelin. This medullated sheath is interrupted at the nodes of
Ranvier, and in each internode is a nucleus lying between the myelin and
the neurolemma. The axis cylinder is the essential conducting structure
of the nerve, while the neurolemma and the myelin act as insulating
agents. The axis cylinder depends for its nutrition on the central
neuron with which it is connected, and from which it originally
developed, and it degenerates if it is separated from its neuron.
The connective-tissue framework of a nerve-trunk consists of the
_perineurium_, or general sheath, which surrounds all the bundles; the
_epineurium_, surrounding individual groups of bundles; and the
_endoneurium_, a delicate connective tissue separating the individual
nerve fibres. The blood vessels and lymphatics run in these
connective-tissue sheaths.
According to Head and his co-workers, Sherren and Rivers, the afferent
fibres in the peripheral nerves can be divided into three systems:--
1. Those which subserve _deep sensibility_ and conduct the impulses
produced by pressure as well as those which enable the patient to
recognise the position of a joint on passive movement (joint-sensation),
and the kinæsthetic sense, which recognises that active contraction of
the muscle is taking place (active muscle-sensation). The fibres of this
system run with the motor nerves, and pass to muscles, tendons, and
joints. Even division of both the ulnar and the median nerves above the
wrist produces little loss of deep sensibility, unless the tendons are
also cut through. The failure to recognise this form of sensibility has
been largely responsible for the conflicting statements as to the
sensory phenomena following operations for the repair of divided nerves.
2. Those which subserve _protopathic_ sensibility--that is, are capable
of responding to painful cutaneous stimuli and to the extremes of heat
and cold. These also endow the hairs with sensibility to pain. They are
the first to regenerate after division.
3. Those which subserve _epicritic_ sensibility, the most highly
specialised, capable of appreciating light touch, _e.g._ with a wisp of
cotton wool, as a well-localised sensation, and the finer grades of
temperature, called cool and warm (72°–104° F.), and of discriminating
as separate the points of a pair of compasses 2 cms. apart. These are
the last to regenerate.
A nerve also exerts a trophic influence on the tissues in which it is
distributed.
The researches of Stoffel on the minute anatomy of the larger nerves,
and the disposition in them of the bundles of nerve fibres supplying
different groups of muscles, have opened up what promises to be a
fruitful field of clinical investigation and therapeutics. He has shown
that in the larger nerve-trunks the nerve bundles for special groups of
muscles are not, as was formerly supposed, arranged irregularly and
fortuitously, but that on the contrary the nerve fibres to a particular
group of muscles have a typical and practically constant position within
the nerve.
In the large nerve-trunks of the limbs he has worked out the exact
position of the bundles for the various groups of muscles, so that in a
cross section of a particular nerve the component bundles can be
labelled as confidently and accurately as can be the cortical areas in
the brain. In the living subject, by using a fine needle-like electrode
and a very weak galvanic current, he has been able to differentiate the
nerve bundles for the various groups of muscles. In several cases of
spastic paralysis he succeeded in picking out in the nerve-trunk of the
affected limb the nerve bundles supplying the spastic muscles, and, by
resecting portions of them, in relieving the spasm. In a case of spastic
contracture of the pronator muscles of the forearm, for example, an
incision is made along the line of the median nerve above the bend of
the elbow. At the lateral side of the median nerve, where it lies in
contact with the biceps muscle, is situated a well-defined and easily
isolated bundle of fibres which supplies the pronator teres, the flexor
carpi radialis, and the palmaris longus muscles. On incising the sheath
of the nerve this bundle can be readily dissected up and its identity
confirmed by stimulating it with a very weak galvanic current. An inch
or more of the bundle is then resected.
INJURIES OF NERVES
Nerves are liable to be cut or torn across, bruised, compressed,
stretched, or torn away from their connections with the spinal medulla.
#Complete Division of a Mixed Nerve.#--Complete division is a common
result of accidental wounds, especially above the wrist, where the
ulnar, median, and radial nerves are frequently cut across, and in
gun-shot injuries.
_Changes in Structure and Function._--The mere interruption of the
continuity of a nerve results in degeneration of its fibres, the myelin
being broken up into droplets and absorbed, while the axis cylinders
swell up, disintegrate, and finally disappear. Both the conducting and
the insulating elements are thus lost. The degeneration in the central
end of the divided nerve is usually limited to the immediate proximity
of the lesion, and does not even involve all the nerve fibres. In the
distal end, it extends throughout the entire peripheral distribution of
the nerve, and appears to be due to the cutting off of the fibres from
their trophic nerve cells in the spinal medulla. Immediate suturing of
the ends does not affect the degeneration of the distal segment. The
peripheral end undergoes complete degeneration in from six weeks to two
months.
The physiological effects of complete division are that the muscles
supplied by the nerve are immediately paralysed, the area to which it
furnishes the sole cutaneous supply becomes insensitive, and the other
structures, including tendons, bones, and joints, lose sensation, and
begin to atrophy from loss of the trophic influence.
#Nerves divided in Amputation.#--In the case of nerves divided in an
amputation, there is an active, although necessarily abortive, attempt
at regeneration, which results in the formation of bulbous swellings at
the cut ends of the nerves. When there has been suppuration, and
especially if the nerves have been cut so as to be exposed in the wound,
these bulbous swellings may attain an abnormal size, and are then known
as "amputation" or "stump neuromas" (Fig. 84).
When the nerves in a stump have not been cut sufficiently short, they
may become involved in the cicatrix, and it may be necessary, on account
of pain, to free them from their adhesions, and to resect enough of the
terminal portions to prevent them again becoming adherent. When this is
difficult, a portion may be resected from each of the nerve-trunks at a
higher level; and if this fails to give relief, a fresh amputation may
be performed. When there is agonising pain dependent upon an ascending
neuritis, it may be necessary to resect the corresponding posterior
nerve roots within the vertebral canal.
[Illustration: FIG. 84.--Stump Neuromas of Sciatic Nerve, excised forty
years after the original amputation by Mr. A. G. Miller.]
#Other Injuries of Nerves.#--_Contusion_ of a nerve-trunk is attended
with extravasation of blood into the connective-tissue sheaths, and is
followed by degeneration of the contused nerve fibres. Function is
usually restored, the conducting paths being re-established by the
formation of new nerve fibres.
When a nerve is _torn across_ or badly _crushed_--as, for example, by a
fractured bone--the changes are similar to those in a divided nerve, and
the ultimate result depends on the amount of separation between the ends
and the possibility of the young axis cylinders bridging the gap.
_Involvement of Nerves in Scar Tissue._--Pressure or traction may be
exerted upon a nerve by contracting scar tissue, or a process of
neuritis or perineuritis may be induced.
When terminal filaments are involved in a scar, it is best to dissect
out the scar, and along with it the ends of the nerves pressed upon.
When a nerve-trunk, such as the sciatic, is involved in cicatricial
tissue, the nerve must be exposed and freed from its surroundings
(_neurolysis_), and then stretched so as to tear any adhesions that may
be present above or below the part exposed. It may be advisable to
displace the liberated nerve from its original position so as to
minimise the risk of its incorporation in the scar of the original wound
or in that resulting from the operation--for example, the radial nerve
may be buried in the substance of the triceps, or it may be surrounded
by a segment of vein or portion of fat-bearing fascia.
_Injuries of nerves resulting from_ #gun-shot wounds# include: (1) those
in which the nerve is directly damaged by the bullet, and (2) those in
which the nerve-trunk is involved secondarily either by scar tissue in
its vicinity or by callus following fracture of an adjacent bone. The
primary injuries include contusion, partial or complete division, and
perforation of the nerve-trunk. One of the most constant symptoms is the
early occurrence of severe neuralgic pain, and this is usually
associated with marked hyperæsthesia.
#Regeneration.#--_Process of Repair when the Ends are in Contact._--_If
the wound is aseptic_, and the ends of the divided nerve are sutured or
remain in contact, they become united, and the conducting paths are
re-established by a regeneration of nerve fibres. There is a difference
of opinion as to the method of regeneration. The Wallerian doctrine is
that the axis cylinders in the central end grow downwards, and enter the
nerve sheaths of the distal portion, and continue growing until they
reach the peripheral terminations in muscle and skin, and in course of
time acquire a myelin sheath; the cells of the neurolemma multiply and
form long chains in both ends of the nerve, and are believed to provide
for the nourishment and support of the actively lengthening axis
cylinders. Another view is that the formation of new axis cylinders is
not confined to the central end, but that it goes on also in the
peripheral segment, in which, however, the new axis cylinders do not
attain maturity until continuity with the central end has been
re-established.
_If the wound becomes infected_ and suppuration occurs, the young nerve
fibres are destroyed and efficient regeneration is prevented; the
formation of scar tissue also may constitute a permanent obstacle to new
nerve fibres bridging the gap.
_When the ends are not in contact_, reunion of the divided nerve fibres
does not take place whether the wound is infected or not. At the
proximal end there forms a bulbous swelling, which becomes adherent to
the scar tissue. It consists of branching axis cylinders running in all
directions, these having failed to reach the distal end because of the
extent of the gap. The peripheral end is completely degenerated, and is
represented by a fibrous cord, the cut end of which is often slightly
swollen or bulbous, and is also incorporated with the scar tissue of
the wound.
#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
compasses; the sensation of pressure, by means of a pencil or other
blunt object; of pain, by pricking 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 (anæsthesia), to pain
(analgesia), 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
(72°–104° F.), and to appreciate as separate impressions the contact of
the two points of a compass--_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 hyperæmia resulting from vaso-motor paralysis is
more persistent, and is associated with swelling of the parts from
œdema--the so-called _angio-neurotic œdema_. 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 anæsthetic 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, massaged,
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 milliampères 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 compass.
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 stitching 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 anæsthesia.
In all these forms there is impaired sensation, rarely amounting to
anæsthesia, 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 retarded or may fail to take place.
Injuries which act abruptly or instantaneously are illustrated in the
crushing 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 mass 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 hyperæsthesia 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 associated 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 constitutional 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 button. 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 arsenic, or from bacterial infections and intoxications
such as occur in diphtheria, gonorrhœa, 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 associated 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 massage, baths,
passive 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 classification 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 circumscribed tumour, or may
take the form of a diffuse fibromatosis.
_The circumscribed 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 hæmorrhage 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 pass through bony canals.
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.
[Illustration: 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 shelling 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 spaces 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 canal.
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 canal, 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 passing through a bony
canal.
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 canal, which press on the spinal
medulla and cause paraplegia.
[Illustration: FIG. 86.--Diffuse enlargement of Nerves in generalised
Neuro-fibromatosis.
(After R. W. Smith.)]
Neuro-fibromatosis is frequently accompanied by _pigmentation of the
skin_ in the form of brown spots or patches scattered over the trunk.
The disease is often stationary for long periods. In progressive cases
the patient becomes exhausted, and usually dies of some intercurrent
affection, particularly phthisis. The treatment is restricted to
relieving symptoms and complications; removal of one of the tumours is
to be strongly deprecated.
In a considerable proportion of cases one of the multiple tumours takes
on the characters of a malignant growth ("secondary malignant neuroma,"
Garrè). This malignant transformation may follow upon injury, or on an
unsuccessful attempt to remove the tumour. The features are those of a
rapidly growing sarcoma involving a nerve-trunk, with agonising pain
and muscular cramps, followed by paralysis from destruction of the
nerve fibres. The removal of the tumour is usually followed by
recurrence, so that high amputation is the only treatment to be
recommended. Metastasis to internal organs is exceptional.
[Illustration: FIG. 87.--Plexiform Neuroma of small Sciatic Nerve, from
a girl æt. 16.
(Mr. Annandale's case.)]
There are other types of neuro-fibromatosis which require brief mention.
_The plexiform neuroma_ (Fig. 87) is a fibromatosis confined to the
distribution of one or more contiguous nerves or of a plexus of nerves,
and it may occur either by itself or along with multiple tumours of the
nerve-trunks and with pigmentation of the skin. The clinical features
are those of an ill-defined swelling composed of a number of tortuous,
convoluted cords, lying in a loose areolar tissue and freely movable on
one another. It is rarely the seat of pain or tenderness. It most often
appears in the early years of life, sometimes in relation to a pigmented
or hairy mole. It is of slow growth, may remain stationary for long
periods, and has little or no tendency to become malignant. It is
usually subcutaneous, and is frequently situated on the head or neck in
the distribution of the trigeminal or superficial cervical nerves. There
is no necessity for its removal, but this may be indicated because of
disfigurement, especially on the face or scalp or because its bulk
interferes with function. When involving the ophthalmic division of the
trigeminus, for example, it may cause enlargement of the upper lid and
proptosis, with danger to the function of the globe. The results of
excision are usually satisfactory, even if the removal is not complete.
[Illustration: FIG. 88.--Multiple Neuro-fibromas of Skin (Molluscum
fibrosum, or Recklinghausen's disease).]
_The cutaneous neuro-fibroma_ or _molluscum fibrosum_ has been shown by
Recklinghausen to be a soft fibroma related to the terminal filaments of
one of the cutaneous nerves (Fig. 88). The disease appears in the form
of multiple, soft, projecting tumours, scattered all over the body,
except the palms of the hands and soles of the feet. The tumours are of
all sizes, some being no larger than a pin's head, whilst many are as
big as a filbert and a few even larger. Many are sessile and others are
distinctly pedunculated, but all are covered with skin. They are mobile,
soft to the touch, and of the consistence of firm fat. In exceptional
cases one of the skin tumours may attain an enormous size and cause a
hideous deformity, hanging down by its own weight in lobulated or folded
masses (pachy-dermatocele). The treatment consists in removing the
larger swellings. In some cases molluscum fibrosum is associated with
pigmentation of the skin and with multiple tumours of the nerve-trunks.
The small multiple tumours rarely call for interference.
[Illustration: FIG. 89.--Elephantiasis Neuromatosa in a woman æt. 28]
_Elephantiasis neuromatosa_ is the name applied by Virchow to a
condition in which a limb is swollen and misshapen as a result of the
extension of a neuro-fibromatosis to the skin and subcutaneous cellular
tissue of the extremity as a whole (Fig. 89). It usually begins in early
life without apparent cause, and it may be associated with multiple
tumours of the nerve-trunks. The inconvenience caused by the bulk and
weight of the limb may justify its removal.
SURGERY OF THE INDIVIDUAL NERVES[6]
[6] We desire here to acknowledge our indebtedness to Mr. James
Sherren's work on _Injuries of Nerves and their Treatment_.
#The Brachial Plexus.#--Lesions of the brachial plexus may be divided
into those above the clavicle and those below that bone.
In the #supra-clavicular injuries#, the violence applied to the head or
shoulder causes over-stretching of the anterior branches (primary
divisions) of the cervical nerves, the fifth, or the fifth and sixth
being those most liable to suffer. Sometimes the traction is exerted
upon the plexus from below, as when a man in falling from a height
endeavours to save himself by clutching at some projection, and the
lesion then mainly affects the first dorsal nerve. There is tearing of
the nerve sheaths, with hæmorrhage, but in severe cases partial or
complete severance of nerve fibres may occur and these give way at
different levels. During the healing process an excess of fibrous tissue
is formed, which may interfere with regeneration.
_Post-anæsthetic paralysis_ occurs in patients in whom, during the
course of an operation, the arm is abducted and rotated laterally or
extended above the head, causing over-stretching of the plexus,
especially of the fifth, or fifth and sixth, anterior branches.
A _cervical rib_ may damage the plexus by direct pressure, the part
usually affected being the medial cord, which is made up of fibres from
the eighth cervical and first dorsal nerves.
When a lesion of the plexus complicates a _fracture of the clavicle_,
the nerve injury is due, not to pressure on or laceration of the nerves
by fragments of bone, but to the violence causing the fracture, and this
is usually applied to the point of the shoulder.
Penetrating _wounds_, apart from those met with in military practice,
are rare.
In the #infra-clavicular injuries#, the lesion most often results from
the pressure of the dislocated head of the humerus; occasionally from
attempts made to reduce the dislocation by the heel-in-the-axilla
method, or from fracture of the upper end of the humerus or of the neck
of the scapula. The whole plexus may suffer, but more frequently the
medial cord is alone implicated.
_Clinical Features._--Three types of lesion result from indirect
violence: the whole plexus; the upper-arm type; and the lower-arm type.
_When the whole plexus is involved_, sensibility is lost over the entire
forearm and hand and over the lateral surface of the arm in its distal
two-thirds. All the muscles of the arm, forearm, and hand are paralysed,
and, as a rule, also the pectorals and spinati, but the rhomboids and
serratus anterior escape. There is paralysis of the sympathetic fibres
to the eye and orbit, with narrowing of the palpebral fissure, recession
of the globe, and the pupil is slow to dilate when shaded from the
light.
The _upper-arm type_--Erb-Duchenne paralysis--is that most frequently
met with, and it is due to a lesion of the fifth anterior branch, or, it
may be, also of the sixth. The position of the upper limb is typical:
the arm and forearm hang close to the side, with the forearm extended
and pronated; the deltoid, spinati, biceps, brachialis, and supinators
are paralysed, and in some cases the radial extensors of the wrist and
the pronator teres are also affected. The patient is unable to supinate
the forearm or to abduct the arm, and in most cases to flex the forearm.
He may, however, regain some power of flexing the forearm when it is
fully pronated, the extensors of the wrist becoming feeble flexors of
the elbow. There is, as a rule, no loss of sensibility, but complaint
may be made of tickling and of pins-and-needles over the lateral aspect
of the arm. The abnormal position of the limb may persist although the
muscles regain the power of voluntary movement, and as the condition
frequently follows a fall on the shoulder, great care is necessary in
diagnosis, as the condition is apt to be attributed to an injury to the
axillary (circumflex) nerve.
The _lower-arm type_ of paralysis, associated with the name of Klumpke,
is usually due to over-stretching of the plexus, and especially affects
the anterior branch of the first dorsal nerve. In typical cases all the
intrinsic muscles of the hand are affected, and the hand assumes the
claw shape. Sensibility is usually altered over the medial side of the
arm and forearm, and there is paralysis of the sympathetic.
_Infra-clavicular injuries_, as already stated, are most often produced
by a sub-coracoid dislocation of the humerus; the medial cord is that
most frequently injured, and the muscles paralysed are those supplied by
the ulnar nerve, with, in addition, those intrinsic muscles of the hand
supplied by the median. Sensibility is affected over the medial surface
of the forearm and ulnar area of the hand. Injury of the lateral and
posterior cords is very rare.
_Treatment_ is carried out on the lines already laid down for nerve
injuries in general. It is impossible to diagnose between complete and
incomplete rupture of the nerve cords, until sufficient time has elapsed
to allow of the establishment of the reaction of degeneration. If this
is present at the end of fourteen days, operation should not be delayed.
Access to the cords of the plexus is obtained by a dissection similar to
that employed for the subclavian artery, and the nerves are sought for
as they emerge from under cover of the scalenus anterior, and are then
traced until the seat of injury is found. In the case of the first
dorsal nerve, it may be necessary temporarily to resect the clavicle.
The usual after-treatment must be persisted in until recovery ensues,
and care must be taken that the paralysed muscles do not become
over-stretched. The prognosis is less favourable in the supra-clavicular
lesions than in those below the clavicle, which nearly always recover
without surgical intervention.
In the _brachial birth-paralysis_ met with in infants, the lesion is due
to over-stretching of the plexus, and is nearly always of the
Erb-Duchenne type. The injury is usually unilateral, it occurs with
almost equal frequency in breech and in vertex presentations, and the
left arm is more often affected than the right. The lesion is seldom
recognised at birth. The first symptom noticed is tenderness in the
supra-clavicular region, the child crying when this part is touched or
the arm is moved. The attitude may be that of the Erb-Duchenne type, or
the whole of the muscles of the upper limb may be flaccid, and the arm
hangs powerless. A considerable proportion of the cases recover
spontaneously. The arm is to be kept at rest, with the affected muscles
relaxed, and, as soon as tenderness has disappeared, daily massage and
passive movements are employed. The reaction of degeneration can rarely
be satisfactorily tested before the child is three months old, but if it
is present, an operation should be performed. After operation, the
shoulder should be elevated so that no traction is exerted on the
affected cords.
#The long thoracic nerve# (nerve of Bell), which supplies the serratus
anterior, is rarely injured. In those whose occupation entails carrying
weights upon the shoulder it may be contused, and the resulting
paralysis of the serratus is usually combined with paralysis of the
lower part of the trapezius, the branches from the third and fourth
cervical nerves which supply this muscle also being exposed to pressure
as they pass across the root of the neck. There is complaint of pain
above the clavicle, and winging of the scapula; the patient is unable to
raise the arm in front of the body above the level of the shoulder or to
perform any forward pushing movements; on attempting either of these the
winging of the scapula is at once increased. If the scapula is compared
with that on the sound side, it is seen that, in addition to the lower
angle being more prominent, the spine is more horizontal and the lower
angle nearer the middle line. The majority of these cases recover if the
limb is placed at absolute rest, the elbow supported, and massage and
galvanism persevered with. If the paralysis persists, the sterno-costal
portion of the pectoralis major may be transplanted to the lower angle
of the scapula.
The long thoracic nerve may be cut across while clearing out the axilla
in operating for cancer of the breast. The displacement of the scapula
is not so marked as in the preceding type, and the patient is able to
perform pushing movements below the level of the shoulder. If the
reaction of degeneration develops, an operation may be performed, the
ends of the nerve being sutured, or the distal end grafted into the
posterior cord of the brachial plexus.
#The Axillary (Circumflex) Nerve.#--In the majority of cases in which
paralysis of the deltoid follows upon an injury of the shoulder, it is
due to a lesion of the fifth cervical nerve, as has already been
described in injuries of the brachial plexus. The axillary nerve itself
as it passes round the neck of the humerus is most liable to be injured
from the pressure of a crutch, or of the head of the humerus in
sub-glenoid dislocation, or in fracture of the neck of the scapula or of
the humerus. In miners, who work for long periods lying on the side, the
muscle may be paralysed by direct pressure on the terminal filaments of
the nerve, and the nerve may also be involved as a result of disease in
the sub-deltoid bursa.
The deltoid is wasted, and the acromion unduly prominent. In recent
cases paralysis of the muscle is easily detected. In cases of long
standing it is not so simple, because other muscles, the spinati, the
clavicular fibres of the pectoral and the serratus, take its place and
elevate the arm; there is always loss of sensation on the lateral aspect
of the shoulder. There is rarely any call for operative treatment, as
the paralysis is usually compensated for by other muscles.
When the _supra-scapular nerve_ is contused or stretched in injuries of
the shoulder, the spinati muscles are paralysed and wasted, the spine of
the scapula is unduly prominent, and there is impairment in the power of
abducting the arm and rotating it laterally.
The _musculo-cutaneous nerve_ is very rarely injured; when cut across,
there is paralysis of the coraco-brachialis, biceps, and part of the
brachialis, but no movements are abolished, the forearm being flexed, in
the pronated position, by the brachio-radialis and long radial extensor
of the wrist; in the supinated position, by that portion of the
brachialis supplied by the radial nerve. Supination is feebly performed
by the supinator muscle. Protopathic and epicritic sensibility are lost
over the radial side of the forearm.
#Radial (Musculo-Spiral) Nerve.#--From its anatomical relationships this
trunk is more exposed to injury than any other nerve in the body. It is
frequently compressed against the humerus in sleeping with the arm
resting on the back of a chair, especially in the deep sleep of
alcoholic intoxication (drunkard's palsy). It may be pressed upon by a
crutch in the axilla, by the dislocated head of the humerus, or by
violent compression of the arm, as when an elastic tourniquet is applied
too tightly. The most serious and permanent injuries of this nerve are
associated with fractures of the humerus, especially those from direct
violence attended with comminution of the bone. The nerve may be crushed
or torn by one of the fragments at the time of the injury, or at a later
period may be compressed by callus.
_Clinical Features._--Immediately after the injury it is impossible to
tell whether the nerve is torn across or merely compressed. The patient
may complain of numbness and tingling in the distribution of the
superficial branch of the nerve, but it is a striking fact, that so long
as the nerve is divided below the level at which it gives off the dorsal
cutaneous nerve of the forearm (external cutaneous branch), there is no
loss of sensation. When it is divided above the origin of the dorsal
cutaneous branch, or when the dorsal branch of the musculo-cutaneous
nerve is also divided, there is a loss of sensibility on the dorsum
of the hand.
The motor symptoms predominate, the muscles affected being the extensors
of the wrist and fingers, and the supinators. There is a characteristic
"drop-wrist"; the wrist is flexed and pronated, and the patient is
unable to dorsiflex the wrist or fingers (Fig. 90). If the hand and
proximal phalanges are supported, the second and third phalanges may be
partly extended by the interossei and lumbricals. There is also
considerable impairment of power in the muscles which antagonise those
that are paralysed, so that the grasp of the hand is feeble, and the
patient almost loses the use of it; in some cases this would appear to
be due to the median nerve having been injured at the same time.
[Illustration: FIG. 90.--Drop-wrist following Fracture of Shaft of
Humerus.]
If the lesion is high up, as it is, for example, in crutch paralysis,
the triceps and anconeus may also suffer.
_Treatment._--The slighter forms of injury by compression recover under
massage, douching, and electricity. If there is drop-wrist, the hand and
forearm are placed on a palmar splint, with the hand dorsiflexed to
nearly a right angle, and this position is maintained until voluntary
dorsiflexion at the wrist returns to the normal. Recovery is sometimes
delayed for several months.
In the more severe injuries associated with fracture of the humerus and
attended with the reaction of degeneration, it is necessary to cut down
upon the nerve and free it from the pressure of a fragment of bone or
from callus or adhesions. If the nerve is torn across, the ends must be
sutured, and if this is impossible owing to loss of tissue, the gap may
be bridged by a graft taken from the superficial branch of the radial
nerve, or the ends may be implanted into the median.
Finally, in cases in which the paralysis is permanent and incurable, the
disability may be relieved by operation. A fascial graft can be employed
to act as a ligament permanently extending the wrist; it is attached to
the third and fourth metacarpal bones distally and to the radius or ulna
proximally. The flexor carpi radialis can then be joined up with the
extensor digitorum communis by passing its tendon through an aperture in
the interosseous membrane, or better still, through the pronator
quadratus, as there is less likelihood of the formation of adhesions
when the tendon passes through muscle than through interosseous
membrane. The palmaris longus is anastomosed with the abductor pollicis
longus (extensor ossis metacarpi pollicis), thus securing a fair amount
of abduction of the thumb. The flexor carpi ulnaris may also be
anastomosed with the common extensor of the fingers. The extensors of
the wrist may be shortened, so as to place the hand in the position of
dorsal flexion, and thus improve the attitude and grasp of the hand.
_The superficial branch of the radial_ (radial nerve) _and the deep
branch_ (posterior interosseous), apart from suffering in lesions of the
radial, are liable to be contused or torn is dislocation of the head of
the radius, and in fracture of the neck of the bone. The deep branch may
be divided as it passes through the supinator in operations on old
fractures and dislocations in the region of the elbow. Division of the
superficial branch in the upper two-thirds of the forearm produces no
loss of sensibility; division in the lower third after the nerve has
become associated with branches from the musculo-cutaneous is followed
by a loss of sensibility on the radial side of the hand and thumb. Wounds
on the dorsal surface of the wrist and forearm are often followed by
loss of sensibility over a larger area, because the musculo-cutaneous
nerve is divided as well, and some of the fibres of the lower lateral
cutaneous branch of the radial.
[Illustration: FIG. 91.--To illustrate the Loss of Sensation produced by
Division of the Median Nerve. The area of complete cutaneous
insensibility is shaded black. The parts insensitive to light touch and
to intermediate degrees of temperature are enclosed within the dotted
line.
(After Head and Sherren.)]
#The Median Nerve# is most frequently injured in wounds made by broken
glass in the region of the wrist. It may also be injured in fractures of
the lower end of the humerus, in fractures of both bones of the forearm,
and as a result of pressure by splints. After _division at the elbow_,
there is impairment of mobility which affects the thumb, and to a less
extent the index finger: the terminal phalanx of the thumb cannot be
flexed owing to the paralysis of the flexor pollicis longus, and the
index can only be flexed at its metacarpo-phalangeal joint by the
interosseous muscles attached to it. Pronation of the forearm is feeble,
and is completed by the weight of the hand. After _division at the
wrist_, the abductor-opponens group of muscles and the two lateral
lumbricals only are affected; the abduction of the thumb can be feebly
imitated by the short extensor and the long abductor (ext. ossis
metacarpi pollicis), while opposition may be simulated by contraction of
the long flexor and the short abductor of the thumb; the paralysis of
the two medial lumbricals produces no symptoms that can be recognised.
It is important to remember that when the median nerve is divided at the
wrist, deep touch can be appreciated over the whole of the area
supplied by the nerve; the injury, therefore, is liable to be over
looked. If, however, the tendons are divided as well as the nerve, there
is insensibility to deep touch. The areas of epicritic and of
protopathic insensibility are illustrated in Fig. 91. The division of
the nerve at the elbow, or even at the axilla, does not increase the
extent of the loss of epicritic or protopathic sensibility, but usually
affects deep sensibility.
[Illustration: FIG. 92.--To illustrate Loss of Sensation produced by
complete Division of Ulnar Nerve. Loss of all forms of cutaneous
sensibility is represented by the shaded area. The parts insensitive to
light touch and to intermediate degrees of heat and cold are enclosed
within the dotted line.
(Head and Sherren.)]
#The Ulnar Nerve.#--The most common injury of this nerve is its division
in transverse accidental wounds just above the wrist. In the arm it may
be contused, along with the radial, in crutch paralysis; in the region
of the elbow it may be injured in fractures or dislocations, or it may
be accidentally divided in the operation for excising the elbow-joint.
When it is injured _at or above the elbow_, there is paralysis of the
flexor carpi ulnaris, the ulnar half of the flexor digitorum profundus,
all the interossei, the two medial lumbricals, and the adductors of the
thumb. The hand assumes a characteristic attitude: the index and middle
fingers are extended at the metacarpo-phalangeal joints owing to
paralysis of the interosseous muscles attached to them; the little and
ring fingers are hyper-extended at these joints in consequence of the
paralysis of the lumbricals; all the fingers are flexed at the
inter-phalangeal joints, the flexion being most marked in the little and
ring fingers--claw-hand or _main en griffe_. On flexing the wrist, the
hand is tilted to the radial side, but the paralysis of the flexor carpi
ulnaris is often compensated for by the action of the palmaris longus.
The little and ring fingers can be flexed to a slight degree by the
slips of the flexor sublimis attached to them and supplied by the median
nerve; flexion of the terminal phalanx of the little finger is almost
impossible. Adduction and abduction movements of the fingers are lost.
Adduction of the thumb is carried out, not by the paralysed adductor
pollicis, but the movement may be simulated by the long flexor and
extensor muscles of the thumb. Epicritic sensibility is lost over the
little finger, the ulnar half of the ring finger, and that part of the
palm and dorsum of the hand to the ulnar side of a line drawn
longitudinally through the ring finger and continued upwards.
Protopathic sensibility is lost over an area which varies in different
cases. Deep sensibility is usually lost over an area almost as extensive
as that of protopathic insensibility.
When the nerve is _divided at the wrist_, the adjacent tendons are also
frequently severed. If divided below the point at which its dorsal
branch is given off, the sensory paralysis is much less marked, and the
injury is therefore liable to be overlooked until the wasting of muscles
and typical _main en griffe_ ensue. The loss of sensibility after
division of the nerve before the dorsal branch is given off resembles
that after division at the elbow, except that in uncomplicated cases
deep sensibility is usually retained. If the tendons are divided as
well, however, deep touch is also lost.
Care must be taken in all these injuries to prevent deformity; a splint
must be worn, at least during the night, until the muscles regain their
power of voluntary movement, and then exercises should be instituted.
#Dislocation of the ulnar nerve# at the elbow results from sudden and
violent flexion of the joint, the muscular effort causing stretching or
laceration of the fascia that holds the nerve in its groove; it is
predisposed to if the groove is shallow as a result of imperfect
development of the medial condyle of the humerus, and by cubitus valgus.
The nerve slips forward, and may be felt lying on the medial aspect of
the condyle. It may retain this position, or it may slip backwards and
forwards with the movements of the arm. The symptoms at the time of the
displacement are some disability at the elbow, and pain and tingling
along the nerve, which are exaggerated by movement and by pressure. The
symptoms may subside altogether, or a neuritis may develop, with severe
pain shooting up the nerve.
The dislocated nerve is easily replaced, but is difficult to retain in
position. In recent cases the arm may be placed in the extended position
with a pad over the condyle, care being taken to avoid pressure on the
nerve. Failing relief, it is better to make a bed for the nerve by
dividing the deep fascia behind the medial condyle and to stitch the
edges of the fascia over the nerve. This operation has been successful
in all the recorded cases.
#The Sciatic Nerve.#--When this nerve is compressed, as by sitting on a
fence, there is tingling and powerlessness in the limb as a whole, known
as "sleeping" of the limb, but these phenomena are evanescent. _Injuries
to the great sciatic nerve_ are rare except in war. Partial division is
more common than complete, and it is noteworthy that the fibres destined
for the peroneal nerve are more often and more severely injured than
those for the tibial (internal popliteal). After complete division, all
the muscles of the leg are paralysed; if the section is in the upper
part of the thigh, the hamstrings are also paralysed. The limb is at
first quite powerless, but the patient usually recovers sufficiently to
be able to walk with a little support, and although the hamstrings are
paralysed the knee can be flexed by the sartorius and gracilis. The
chief feature is drop-foot. There is also loss of sensation below the
knee except along the course of the long saphenous nerve on the medial
side of the leg and foot. Sensibility to deep touch is only lost over a
comparatively small area on the dorsum of the foot.
#The Common Peroneal (external popliteal) nerve# is exposed to injury
where it winds round the neck of the fibula, because it is superficial
and lies against the unyielding bone. It may be compressed by a
tourniquet, or it may be bruised or torn in fractures of the upper end
of the bone. It has been divided in accidental wounds,--by a scythe, for
example,--in incising for cellulitis, and in performing subcutaneous
tenotomy of the biceps tendon. Cases have been observed of paralysis of
the nerve as a result of prolonged acute flexion of the knee in certain
occupations.
When the nerve is divided, the most obvious result is "drop-foot"; the
patient is unable to dorsiflex the foot and cannot lift his toes off the
ground, so that in walking he is obliged to jerk the foot forwards and
laterally. The loss of sensibility depends upon whether the nerve is
divided above or below the origin of the large cutaneous branch which
comes off just before it passes round the neck of the fibula. In course
of time the foot becomes inverted and the toes are pointed--pes
equino-varus--and trophic sores are liable to form.
#The Tibial (internal popliteal) nerve# is rarely injured.
#The Cranial nerves# are considered with affections of the head and neck
(Vol. II.).
NEURALGIA
The term neuralgia is applied clinically to any pain which follows the
course of a nerve, and is not referable to any discoverable cause. It
should not be applied to pain which results from pressure on a nerve by
a tumour, a mass of callus, an aneurysm, or by any similar gross lesion.
We shall only consider here those forms of neuralgia which are amenable
to surgical treatment.
#Brachial Neuralgia.#--The pain is definitely located in the
distribution of one of the branches or nerve roots, is often
intermittent, and is usually associated with tingling and disturbance of
tactile sensation. The root of the neck should be examined to exclude
pressure as the cause of the pain by a cervical rib, a tumour, or an
aneurysm. When medical treatment fails, the nerve-trunks may be injected
with saline solution or recourse may be had to operative measures, the
affected cords being exposed and stretched through an incision in the
posterior triangle of the neck. If this fails to give relief, the more
serious operation of resecting the posterior roots of the affected
nerves within the vertebral canal may be considered.
_Neuralgia of the sciatic nerve_--#sciatica#--is the most common form of
neuralgia met with in surgical practice.
It is chiefly met with in adults of gouty or rheumatic tendencies who
suffer from indigestion, constipation, and oxaluria--in fact, the same
type of patients who are liable to lumbago, and the two affections are
frequently associated. In hospital practice it is commonly met with in
coal-miners and others who assume a squatting position at work. The
onset of the pain may follow over-exertion and exposure to cold and wet,
especially in those who do not take regular exercise. Any error of diet
or indulgence in beer or wine may contribute to its development.
The essential symptom is paroxysmal or continuous pain along the course
of the nerve in the buttock, thigh, or leg. It may be comparatively
slight, or it may be so severe as to prevent sleep. It is aggravated by
movement, so that the patient walks lame or is obliged to lie up. It is
aggravated also by any movement which tends to put the nerve on the
stretch, as in bending down to put on the shoes, such movements also
causing tingling down the nerve, and sometimes numbness in the foot.
This may be demonstrated by flexing the thigh on the abdomen, the knee
being kept extended; there is no pain if the same manœuvre is repeated
with the knee flexed. The nerve is sensitive to pressure, the most
tender points being its emergence from the greater sciatic foramen, the
hollow between the trochanter and the ischial tuberosity, and where the
common peroneal nerve winds round the neck of the fibula. The muscles of
the thigh are often wasted and are liable to twitch.
The clinical features vary a good deal in different cases; the affection
is often obstinate, and may last for many weeks or even months.
In the sciatica that results from neuritis and perineuritis, there is
marked tenderness on pressure due to the involvement of the nerve
filaments in the sheath of the nerve, and there may be patches of
cutaneous anæsthesia, loss of tendon reflexes, localised wasting of
muscles, and vaso-motor and trophic changes. The presence of the
reaction of degeneration confirms the diagnosis of neuritis. In
long-standing cases the pain and discomfort may lead to a postural
scoliosis (_ischias-scoliotica_).
_Diagnosis._--Pain referred along the course of the sciatic nerve on one
side, or, as is sometimes the case, on both sides, is a symptom of
tumours of the uterus, the rectum, or the pelvic bones. It may result
also from the pressure of an abscess or an aneurysm either inside the
pelvis or in the buttock, and is sometimes associated with disease of
the spinal medulla, such as tabes. Gluteal fibrositis may be mistaken
for sciatica. It is also necessary to exclude such conditions as disease
in the hip or sacro-iliac joint, especially tuberculous disease and
arthritis deformans, before arriving at a diagnosis of sciatica. A
digital examination of the rectum or vagina is of great value in
excluding intra-pelvic tumours.
_Treatment_ is both general and local. Any constitutional tendency, such
as gout or rheumatism, must be counteracted, and indigestion, oxaluria,
and constipation should receive appropriate treatment. In acute cases
the patient is confined to bed between blankets, the limb is wrapped in
thermogene wool, and the knee is flexed over a pillow; in some cases
relief is experienced from the use of a long splint, or slinging the leg
in a Salter's cradle. A rubber hot-bottle may be applied over the seat
of greatest pain. The bowels should be well opened by castor oil or by
calomel followed by a saline. Salicylate of soda in full doses, or
aspirin, usually proves effectual in relieving pain, but when this is
very intense it may call for injections of heroin or morphin. Potassium
iodide is of benefit in chronic cases.
Relief usually results from bathing, douching, and massage, and from
repeated gentle stretching of the nerve. This may be carried out by
passive movements of the limb--the hip being flexed while the knee is
kept extended; and by active movements--the patient flexing the limb at
the hip, the knee being maintained in the extended position. These
exercises, which may be preceded by massage, are carried out night and
morning, and should be practised systematically by those who are liable
to sciatica.
Benefit has followed the injection into the nerve itself, or into the
tissues surrounding it, of normal saline solution; from 70–100 c.c. are
injected at one time. If the pain recurs, the injection may require to
be repeated on many occasions at different points up and down the nerve.
Needling or acupuncture consists in piercing the nerve at intervals in
the buttock and thigh with long steel needles. Six or eight needles are
inserted and left in position for from fifteen to thirty minutes.
In obstinate and severe cases the nerve may be _forcibly stretched_.
This may be done bloodlessly by placing the patient on his back with the
hip flexed to a right angle, and then gradually extending the knee until
it is in a straight line with the thigh (Billroth). A general anæsthetic
is usually required. A more effectual method is to expose the nerve
through an incision at the fold of the buttock, and forcibly pull upon
it. This operation is most successful when the pain is due to the nerve
being involved in adhesions.
#Trigeminal Neuralgia.#--A severe form of epileptiform neuralgia occurs
in the branches of the fifth nerve, and is one of the most painful
affections to which human flesh is liable. So far as its pathology is
known, it is believed to be due to degenerative changes in the semilunar
(Gasserian) ganglion. It is met with in adults, is almost invariably
unilateral, and develops without apparent cause. The pain, which occurs
in paroxysms, is at first of moderate severity, but gradually becomes
agonising. In the early stages the paroxysms occur at wide intervals,
but later they recur with such frequency as to be almost continuous.
They are usually excited by some trivial cause, such as moving the jaws
in eating or speaking, touching the face as in washing, or exposure to a
draught of cold air. Between the paroxysms the patient is free from
pain, but is in constant terror of its return, and the face wears an
expression of extreme suffering and anxiety. When the paroxysm is
accompanied by twitching of the facial muscles, it is called _spasmodic
tic_.
The skin of the affected area may be glazed and red, or may be pale and
moist with inspissated sweat, the patient not daring to touch or wash
it.
There is excessive tenderness at the points of emergence of the
different branches on the face, and pressure over one or other of these
points may excite a paroxysm. In typical cases the patient is unable to
take any active part in life. The attempt to eat is attended with such
severe pain that he avoids taking food. In some cases the suffering is
so great that the patient only obtains sleep by the use of hypnotics,
and he is often on the verge of suicide.
_Diagnosis._--There is seldom any difficulty in recognising the disease.
It is important, however, to exclude the hysterical form of neuralgia,
which is characterised by its occurrence earlier in life, by the pain
varying in situation, being frequently bilateral, and being more often
constant than paroxysmal.
_Treatment._--Before having recourse to the measures described below, it
is advisable to give a thorough trial to the medical measures used in
the treatment of neuralgia.
_The Injection of Alcohol into the Nerve._--The alcohol acts by
destroying the nerve fibres, and must be brought into direct contact
with them; if the nerve has been properly struck the injection is
followed by complete anæsthesia in the distribution of the nerve. The
relief may last for from six months to three years; if the pain returns,
the injection may be repeated. The strength of the alcohol should be 85
per cent., and the amount injected about 2 c.c.; a general, or
preferably a local, anæsthetic (novocain) should be employed
(Schlösser); the needle is 8 cm. long, and 0.7 mm. in diameter. The
severe pain which the alcohol causes may be lessened, after the needle
has penetrated to the necessary depth, by passing a few cubic
centimetres of a 2 per cent. solution of _novocain-suprarenin_ through
it before the alcohol is injected. The treatment by injection of alcohol
is superior to the resection of branches of the nerve, for though
relapses occur after the treatment with alcohol, renewed freedom from
pain may be obtained by its repetition. The ophthalmic division should
not, however, be treated in this manner, for the alcohol may escape into
the orbit and endanger other nerves in this region. Harris recommends
the injection of alcohol into the semilunar ganglion.
_Operative Treatment._--This consists in the removal of the affected
nerve or nerves, either by resection--_neurectomy_; or by a combination
of resection with twisting or tearing of the nerve from its central
connections--_avulsion_. To prevent the regeneration of the nerve after
these operations, the canal of exit through the bone should be
obliterated; this is best accomplished by a silver screw-nail driven
home by an ordinary screw-driver (Charles H. Mayo).
When the neuralgia involves branches of two or of all three trunks, or
when it has recurred after temporary relief following resection of
individual branches, the _removal of the semilunar ganglion_, along with
the main trunks of the maxillary and mandibular divisions, should be
considered.
The operation is a difficult and serious one, but the results are
satisfactory so far as the cure of the neuralgia is concerned. There is
little or no disability from the unilateral paralysis of the muscles of
mastication; but on account of the insensitiveness of the cornea, the
eye must be protected from irritation, especially during the first month
or two after the operation; this may be done by fixing a large
watch-glass around the edge of the orbit with adhesive plaster.
If the ophthalmic branch is not involved, neither it nor the ganglion
should be interfered with; the maxillary and mandibular divisions should
be divided within the skull, and the foramen rotundum and foramen ovale
obliterated.