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.