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.