CHAPTER X

TRIGEMINAL NEURALGIA

Neuralgia of the fifth or trigeminal nerve is, in its varying degrees, of frequent occurrence. In its cause, manifestations, and progress, it offers so wide a field for discussion that the question must be focussed down by means of some simple form of classification such as enables one to include the majority of cases that come before one’s observation.

For all practical purposes, the following types will be sufficiently inclusive:--

Neuralgia minor.

Neuralgia major.

Hysterical neuralgia.

NEURALGIA MINOR

This variety is almost invariably dependent in its development on some exciting cause. In some cases this cause is readily demonstrated, in others great difficulty may be experienced before the source is discovered.

These secondary neuralgias may be regarded as resulting from the following injuries and diseases.

Diseases of the tongue, fauces, and pharynx. For example, the pain referred to the lingual nerve in epithelioma of the tongue.

Diseases and injuries of the maxillæ. For example, the neuralgia associated with dental caries.

Injuries and diseases of the nose and its accessory cavities. For example, the infra-orbital pain experienced in empyema of the antrum.

Injuries and diseases of the bones of the skull. For example, the pain referred along the course of those nerves emerging through the basal foramina involved in a fracture of the base of the skull.

Errors of refraction. For example, neuralgia of the supra-orbital nerve.

Anæmia, influenza, alcoholism, Bright’s disease, cold, worry, malaria (brow-ague), rheumatism, &c.

But slight allusion need be made to the _symptomatology_ of neuralgia minor--the conditions are more or less familiar to every one. The pain, though usually most intense in that particular branch of the nerve which is most intimately related to the source of the neuralgia, is often referred to other branches of the same nerve-trunk, and sometimes to an entirely different nerve. Thus, in the case of an epithelioma of the tongue, the pain, though perhaps most acute in the region supplied by the lingual nerve, is nevertheless frequently referred to the ear along the course and distribution of the chorda tympani.

The pain is more or less continuous, often associated with exacerbations, but seldom paroxysmal. The patient frequently complains of heat and tenderness over the areas supplied by the nerve in question and, in almost every instance, there are points of special tenderness corresponding as a rule to the emergence of the nerve-trunk through some osseous foramen. Again, some relief may be obtained by the application of pressure over the site of that foramen. For example, neuralgia dependent on antral empyema is most acute in the region of the infra-orbital foramen, and relief may be experienced by pressure applied over that foramen.

In the event of failure to discover an exciting cause, some difficulty may be experienced in coming to a correct conclusion as to whether the case belongs to the minor types of neuralgia, or should be relegated to the more serious group of neuralgia major (tic doloreux). In general, however, the neuralgias minor may be distinguished from the major variety by the following features:--

(1) The presence of some detectable forms of nerve-irritation. In the neuralgias major there may be no such cause.

(2) The relief of symptoms on the successful treatment of the cause.

(3) The relative absence of those paroxysmal attacks which are so typical of neuralgia major.

(4) The infrequence of severe vaso-motor, trophic, and sensory changes in the regions supplied by the nerve affected. Such changes are more or less constant in neuralgia major.

(5) The wide distribution of the pain and its reference to other nerves, with no clear line of demarcation from neighbouring areas supplied by totally different nerves. In neuralgia major the pain, though often involving both second and third divisions of the fifth nerve, is referred to the areas supplied by those nerves only, with a clear line of demarcation from neighbouring regions.

In cases of neuralgia of doubtful origin one can only observe the effect of treatment and be guided by the results obtained.

=Treatment.= The source of the neuralgia requires primary consideration. When this has been rectified the patient should be treated after general medical principles. In the event of failure at relief, we have two other strings to our bow--alcohol injections, and neurectomy of the nerve involved. Alcohol injections are dealt with later. Neurectomy--after Thiersch’s method of avulsion--is greatly preferable to all the older methods of neurotomy, nerve-stretching, and nerve-division. These older methods brought about in their train but transitory alleviation of pain.

=Neurectomy of the inferior dental nerve.= A transverse incision is made through the skin and subcutaneous tissues at the level of junction between horizontal and vertical rami of the jaw, extending from the anterior border of the vertical ramus to the posterior border of the same. The tissues are retracted and the masseter muscle exposed. The muscle fibres are split in the vertical direction and the bone laid bare. A ¹⁄₂ inch trephine is applied, and a disk of bone removed so as to expose the inferior dental nerve at its entrance into the inferior dental canal. The nerve is freed from the corresponding artery, divided at the centre of exposure, and the two ends seized with forceps, twisted and avulsed in such a manner as to destroy and remove the maximum number of nerve-fibres. The disk of bone is replaced, the muscle fibres brought together with a few catgut sutures, and the margins of the skin incision approximated.

=Exposure of the infra-orbital nerve.= A curved incision is made through the skin and subcutaneous tissues parallel to and below the infra-orbital margin, the tissues retracted, and the small muscles overlying the infra-orbital foramen divided or retracted so as to allow exposure of the foramen. The nerve is isolated and divided. The peripheral end is seized with forceps and avulsed. The central end may be treated after similar fashion, or, preferably, again exposed in the infra-orbital groove or canal, the tissues being peeled away from the floor of the orbit and the nerve sought for as it traverses the infra-orbital canal. With this object in view, it may be necessary to gently break away the osseous roof of the canal before the nerve can be exposed. It is then lifted up with a small hook, drawn through the infra-orbital foramen, seized with forceps, and avulsed in such a manner as to be torn away somewhere in the region of the spheno-maxillary fossa. The wound is then sewn up.

=Exposure of the supra-orbital nerve.= The nerve is exposed through a curved incision parallel to the supra-orbital margin, and so planned as to be concealed by the eyebrow. The fibres of the orbicularis palpebrarum are separated and the foramen identified. The nerve is separated from its artery, divided, the peripheral portion avulsed, and the central portion again exposed as it courses along the roof of the orbit. For this purpose the tissues of the upper lid are detached from the supra-orbital margin, the nerve delivered with the aid of a small hook, brought out through the foramen, and avulsed in such a manner as to be torn away somewhere in the region of the sphenoidal fissure. The wound is then sewn up.

NEURALGIA MAJOR

Neuralgia major originates most commonly in the third division of the nerve, less frequently in the second, and rarely in the first. Whichever division be primarily affected, there is a very general tendency for other branches to become involved, and this in a very definite way--the pain spreading centrally from the nerve first involved, radiating to other nerve-trunks so soon as they shall be reached. Thus, pain originating in the inferior dental branch of the third division spreads to the lingual and other branches of that division and then involves the second division. Fortunately, whether the trouble originates in the third or second divisions, the ophthalmic tends to escape or to become less seriously involved--a fortunate circumstance considering the terrible conditions associated with neuritis of that nerve, the disastrous results on cornea, conjunctiva, &c.

The disease is undoubtedly of a progressive nature, originating without rhyme or reason. It seldom becomes evident before the ages of 45 to 55, affecting both rich and poor alike.

Wilfred Harris[69] collected 265 cases, and showed that the disease was slightly more common in men than in women--144 to 131. There appeared to be some predilection for the disease to involve the right side in preference to the left--179 to 80. In 6 cases the affection was bilateral.

Trigeminal neuralgia does not in itself lead to fatal results, but the continuous pain, the want of sleep, and the difficulty experienced in taking sufficient nourishment soon reduce the patient to such a miserable condition that, unless relieved by the surgeon, amelioration is sought in morphia or release in death.

Before proceeding further it will be convenient to enumerate certain points aiding in the differential diagnosis between the true and hysterical forms of trigeminal neuralgia.

_True Neuralgia._ _Hysterical Neuralgia._

Patient old, probably over 50, Patient young, more commonly of the and more commonly of the male female sex. sex.

Pain paroxysmal. Pain severe for long periods together.

Vaso-motor, trophic and sensory All these changes very rare. changes common.

Pain strictly unilateral and Pain variable in distribution, constant in site. radiating irregularly to the opposite side of the face.

The =pathology= of tic doloreux is most obscure. The parts requiring examination are the peripheral nerve-trunks, the ganglion, the sensory root, and the central nervous system. The last two regions may be excluded, not only on the ground that research has failed to show any constant structural changes, but also because the removal of the ganglion may be regarded as curative of the disease. The ganglion itself and the peripheral nerve-trunks remain for investigation.

In the peripheral nerve-fibres no constant material changes have been observed. The epineurium, on the other hand, is almost invariably shrunken and sclerosed. Considerable stress might be laid on this fact unless it were also taken into consideration that the nerves were examined in patients who had suffered from major neuralgia for prolonged periods of time. Similar changes have also been observed in patients who have never exhibited neuralgic symptoms.

In the ganglion itself the following changes have been observed:--(1) arterio-sclerosis; (2) alteration in the character of the nerve-fibres traversing the ganglion; and (3) adhesions between the ganglion and the surrounding parts. All these changes, however, are so inconstant that but little importance can be attached to them.

At the present time there is a disposition to regard trigeminal neuralgia in the light of an ascending neuritis, originating peripherally and ascending towards the Gasserian ganglion. Sir Victor Horsley first pointed out that the ganglion acts as a barrier to the further upward spread of the affection. This is proved by the success obtained in the removal of the ganglion.

Symptomatology.

_Pain._ The onset of pain may be preceded by premonitory symptoms such as tinglings, throbbings, and burning sensations in the parts subsequently involved, whilst, in the earlier stages of the disease, the pain may be more or less localized to the site of emergence of the nerve from an osseous foramen.

In the earlier stages also the attacks, though severe, are paroxysmal, of short duration, perhaps not lasting more than half a minute, and definitely localized to some special nerve-trunk. During the periods of remission the patient feels quite well. Gradually the pain increases in severity, the periods of remission shorten, and the pain in its distribution becomes more widespread, the neuritis--or whatever the process may be--spreading centrally and radiating along the course and distribution of such branches of the nerve as shall be encountered.

Paroxysms are a marked feature, occasionally of so severe a nature that the patient falls to the ground as if struck by lightning, recovering after a variable period of time.

In the later stages of the disease the pain may be almost continuous, and the condition of the patient is truly miserable.

The attacks are often ushered in by the slightest stimulus--talking, mastication of food, draughts, emotion, &c.--and, in order to avoid the occurrence as far as possible, the patient abstains from talking, dreads eating, &c. Dribbling from the mouth may be observed in those cases in which the patient finds some relief in keeping the mouth open. It is also frequently seen during the height of the paroxysm. At such stages the patient is collapsed, with feeble pulse, shallow respiration, the temperature subnormal, and the skin clammy. The attacks occur both during the day and the night, sleep fails, and the body nutrition suffers.

The site at which the pain originates can often be fixed by the patient himself. Occasionally relief may be attained by pressure applied over some particular part, by heat or by cold, or by some other method discovered by the patient himself.

The attacks are often accompanied by twitchings of the muscles supplied by the facial nerve, and, according to some investigators, by fibrillary twitchings of the muscles of the region affected.

In the later stages, wasting of the muscles may be observed.

_Vaso-motor and trophic changes._ The skin and mucous membrane supplied by the nerve involved become hyperæmic and hyperæsthetic, and, in the more chronic cases, these changes may be associated with œdema of the subcutaneous tissues--the clinical picture now closely resembling that observed in some cases of angio-neurotic œdema.

Other symptoms of similar nature are herpes, increased salivation, furred tongue (on the side of the lesion), sweating of the skin, lacrimation, conjunctivitis, and keratitis.

_General decline in health._ This depends, not only on the difficulty experienced in taking sufficient nourishment, but also on the moral effect produced by the more or less continuous pain. In the more severe cases emaciation is rapid.

Treatment.

1. _Therapeutic remedies._ The following drugs have been recommended.

Quinine, in large and increasing doses.

Arsenic, given in a similar fashion.

Gelsemium, in toxic doses, every few hours until tinglings in the fingers and nausea show that the drug has been pushed far enough (Sir Victor Horsley).

Methylene blue, in three-grain doses (Sir Watson Cheyne).

Iron, antipyrin, strychnine, cannabis indica, &c.

Morphia. This drug is undoubtedly beneficial in its results, but the habitual use thereof is strongly contra-indicated, not only because of the temporary benefit received, but also because of the necessary increase in the quantity required to alleviate the pain. If persistently used the patient gradually develops the morphia habit.

Some of these remedies suffice for the neuralgias minor, but with regard to their action in cases of neuralgia major, their effect may be summed up as follows: ‘True tic doloreux has been the therapeutic despair of most physicians and surgeons,’[70] and ‘too often the operation is put off till the patient is addicted to the morphia habit, depleted in strength and vitality by drugs, sleepless nights, and years of intense suffering’.[71]

Until quite recently, with the exception of these medicinal remedies, the only other methods at our disposal in the treatment of trigeminal neuralgia were Gasserian ganglion removal and other intracranial operations on the three divisions of the fifth nerve. In 1906, however, Schlösser[72] of Munich advocated the injection of alcohol into the region of those foramina at the base of the skull through which the nerve trunks emerged. As the result of these injections it was stated that, although some slight degree of cutaneous anæsthesia frequently resulted, yet that it was usually of an unimportant and transient character, and that the pain subsided and finally ceased, remaining absent for a variable period of time, usually about ten months. In the event of recurrence the injection was repeated, each period of recurrent pain being less intense and less prolonged, whilst the periods of remission increased proportionately.

Whilst it is clear from the results obtained by those who have followed in Schlösser’s footsteps, that alcohol injections are, as a rule, reasonably satisfactory, yet it must be clearly understood that beneficial results are not always observed, and that in the event of failure the more radical intracranial operations must be carried out.

The technique of alcohol injections.

_Question of anæsthetic._ Freezing of the skin or other method of local anæsthesia suffices to allow of the painless introduction of the needle. A general anæsthetic should be avoided wherever possible, as the burning sensation experienced by the patient when the nerve-trunk is encountered greatly assists the accuracy of introduction.

_The needle._ The needle should be stout--10 cm. long, 1·5 cm. in diameter, and graduated in centimetres up to 5 cm., and provided with a blunt stilette.

_Introduction._ The skin is cleansed, the stilette slightly withdrawn, and the needle introduced. After puncture of the skin the stilette is pushed home, all further introduction being carried out with the blunt advancing point. When in position, the stilette is withdrawn, and a glass syringe, ready filled with alcohol, fitted to the needle and the injection made.

_The solution._ Purves Stewart recommends the injection of 1-1·5 c.cm. of the following solution:--

Beta eucaine, 2 grains Absolute alcohol, 6 drs. Distilled water to the ounce.

Wilfred Harris advises 90 per cent. alcohol, preceded by a 2 per cent. solution eucaine. He urges that two or three drops should be injected slowly, and if the needle be correctly placed a sharp burning pain will instantly be felt over the area of the distribution of the nerve, lasting fifteen seconds or so and then dying away. Two or three more drops are then injected, and thus ‘a few drops at a time, from 1 to 1·5 c.cm. are injected, the pain produced with each succeeding push of the syringe being less and less’.

To reach the _foramen ovale_ (third division), the needle is introduced through the cheek behind the last molar tooth, at the lower border of the zygoma, at a point 2¹⁄₂ cm. in front of the descending root of the zygoma. The blunt needle penetrates the masseter muscle and the posterior part of the temporal muscle. It is then directed backwards and slightly upwards till it impinges on the skull at the external pterygoid plate. It is then pushed on, upwards and backwards, till it enters the foramen ovale at a depth usually of about 4 cm. from the zygoma. In case of difficulty in passing the needle through the sigmoid notch of the jaw the mouth should be widely opened.

If the needle be directed too low it may penetrate the pharyngeal wall or the Eustachian tube; if too far back, the middle meningeal artery.

To reach the _foramen rotundum_ (second division)--a rather more difficult procedure--it is necessary to find the posterior border of the orbital process of the malar bone, prolonging this line downwards to the lower border of the zygoma and inserting the needle ¹⁄₂ cm. posterior to this point. The needle is pushed horizontally inwards and the point directed slightly upwards, the foramen being reached in the pterygo-maxillary fossa at a depth of about 3 cm. from the zygoma. The needle, for an average-sized skull, should never penetrate deeper than 5