The TREATMENT consists, at the outset, in rest and position, the local abstraction of blood (in cases where the nerve-trunk is swollen and tender), and the administration of such drugs as we suppose act favorably upon the inflammation of the nerves. Salicylic acid or salicylate of sodium seem to act beneficially in relieving the severe pains in the outset of the disease. Iodide of potassium, gradually increased until large doses are taken, has, in the experience of the writer, seemed to beneficially modify the course of multiple neuritis. The necessary relief of pain is best obtained by hypodermic injections of morphia, supplemented by heat applied to the affected nerves. To these means may be added rubbing with chloroform and applying to the painful parts cloths dipped in a 5 per cent. solution of carbolic acid. After the acute stage has been passed and in chronic cases, just as soon as we have reason to suppose that the degenerative process in the nerves has come to a standstill, we possess in the use of electricity the means of hastening the regeneration of the nerve-fibres, strengthening the paralyzed muscles, and restoring the sensation. The galvanic current is to be preferred, and it is to be applied to the crippled nerves and muscles—sometimes stable for its electrolytic action, sometimes interrupted to obtain its exciting and stimulating effect. The excitement to nerves and muscles by the use of the faradic current has also its uses in hastening recovery. Protracted treatment and much patience are required to overcome contractions and restore the nerves and muscles, and the effects of the disease may be seen for a long time in the weakness and diminished electric reaction of the muscles.
Anæsthesia of Peripheral Origin.
A prominent and important symptom of the lesion of peripheral nerves is the diminution and loss of cutaneous sensibility. Besides the anæsthesia caused by the affections of the fibres themselves, which has been touched upon in the preceding pages, it may be produced by morbid states of the peripheral end-organs or cutaneous terminations of the nerves. Cold applied to a nerve-trunk may produce alterations which for days after cause numbness and paræsthesia in the surface to which it is distributed, and the application of cold to the surface of the body, as we know from common observation, causes blunting of the cutaneous sensations, especially that of touch. In this way, from exposure to the atmosphere at low temperatures, to cold winds, or by the immersion of the body in cold water, the end-organs of the nerves in the skin are morbidly affected, and anæsthesia results, the so-called rheumatic anæsthesia. Many substances, as acids, notably carbolic acid, alkalies, narcotics, etc., act upon the cutaneous end-organs in a way to destroy their capacity for receiving or transmitting impressions and produce a more or less persistent anæsthesia of the skin. In the anæsthesia so often observed in the hands and forearms of washerwomen we have an example of the action probably of several of these causes, as the frequent plunging of the hands into cold water and the action upon the skin of alkalies and alkaline soaps. The diminution or interruption of the circulation through the skin, as in ischæmia from spasm of the minute arteries due to an affection of the vaso-motor nerves, is also a cause of cutaneous anæsthesia. In lepra anæsthetica (Spedalskhed) the cutaneous anæsthesia is dependent upon a neuritis of the minute branches in the skin. The local anæsthesia met with so often in syphilis, though its pathology is doubtful, is not improbably sometimes caused by an affection of the peripheral nerves (neuritis?) and their end-organs. After many acute diseases, diphtheria, typhoid fever, etc., we have cutaneous anæsthesia in connection with muscular paralysis, the cause of both being a neuritis. The patient is made aware of the loss of sensation by some interference with his usual sensations and movements. If he puts a glass to his lips, the sensation is as if a bit were broken out of the rim; his accustomed manipulations are awkward, because of the want of distinct appreciation of the objects he holds; he fumbles in buttoning his clothes or he stumbles unless looking to his steps. An examination, nevertheless, almost always reveals that the anæsthesia is greater than would have been supposed from the subjective feelings of the patient; indeed, cases occur in which he is not aware of an existing defect of sensation. But a careful examination is not only required to determine the extent, but by it alone can we arrive at a knowledge of the quality of the anæsthesia—viz. whether there is a loss of all of the different kinds of sensation, whether they are affected in an unequal degree, or whether some have entirely escaped. Thus we must test for the acuteness of the simple sense of touch by comparing the sensations elicited by the contact of small surfaces of unequal size, as the point and head of a pin or pencil, observing the appreciation by touch of the patient for different substances, as woollen, silk, linen, cloth, or comparing the sensation of the anæsthesic part with the same part on the opposite healthy side of the body. The sense of locality and space may be examined by placing at the same instant upon the skin of the patient, his eyes being closed, two points (the anæsthesiometer or the points of a compass), and observing his capacity for appreciating the impression as double. As there is an enormous difference of acuteness of the space-sense in the skin of different parts of the body (see textbooks of physiology)—ranging from the tip of the tongue, where the touch of two points separated 1.2 mm. gives a double sensation, to the thigh, where the points must be separated 77 mm. to be felt as two—we must be careful to consider in making the examination the normal space-perception of the region. Care must be taken not to repeat the test too often, as a rapid education of the surface to a more delicate appreciation of the impressions is the result. In certain abnormal conditions from spinal disease we have a condition of polyæsthesia in which the impression of one point is felt as two or more. The sense by which we appreciate the pressure of objects must be tested by placing upon the surface to be examined, in succession, objects of different weight, care being taken to have the area which touches the skin and the temperature the same in each. The parts to be tested must be firmly supported, and all muscular contraction on the part of the patient prevented. The temperature sense is examined by the application of hot and cold water or bodies of different temperature. We sometimes meet with a perversion of this sense in which the application of a cold surface to the skin gives the sensation of warmth, and the contrary. In testing the sense of temperature and the sense of pressure it is not the absolute capacity of appreciating on the part of the patient that we investigate, but the power of discriminating between different degrees of temperature or pressure. The sense of pain must likewise be tested, since morbid conditions occur in which it may be caused more readily than is normal by exciting the cutaneous nerves, and that, too, in parts which have in a great measure or quite lost the sense of touch; or, on the other hand, touch may be retained, while irritation of the skin can excite no feeling of pain (analgesia). We have in the faradic current an excellent means of testing the cutaneous sensibility, inasmuch as it excites the skin over the various parts of the body about equally, and it can be employed in very gradually increasing or decreasing strength. Its effects on the affected part must be compared with those produced on the healthy surface of other parts of the patient's body or on healthy individuals.
Frequently accompanying cutaneous anæsthesia, but constituting no part of it, are various paræsthesiæ, as formication, pins and needles, burning, etc. Pain, sometimes of great intensity, is not infrequently connected with it (anæsthesia dolorosa). The paræsthesiæ and pain are the result of irritation in some portion of the conducting tracts, and, together with the trophic changes so often seen in connection with nerve-injuries, they have been already considered under that head.
It is a very important point to make the diagnosis between central and peripheral anæsthesia, but it is often a matter of great difficulty, and sometimes not to be made at all. The history of the case must be carefully considered, and an examination made for symptoms of brain or spinal disease, the existence of nerve lesions, or if there is a history of toxic influences, etc. In peripheral anæsthesia the reflexes which may be normally excited from the affected surface are wanting, in contradistinction to anæsthesia of central origin, in which they are most generally retained or even increased. Concomitant trophic changes speak strongly for a peripheral origin, as do also paralysis and atrophy of muscles. Loss of some of the forms of sensation, with retention of others—i.e. partial paralysis of sensation—indicate a central origin.
The TREATMENT of peripheral anæsthesia must look, in the first place, to removal, if possible, of its cause, and the treatment of diseased conditions, if any exist, of the nerve-trunks, as neuritis, mechanical injuries, etc. Local applications of a stimulating character may be advantageously used upon the anæsthesic parts. By far the most effective stimulant to the diseased nerves is the faradic or galvanic current, and it should be used in the way that will produce the greatest amount of excitation in the cutaneous end-organs. This is best done by applying the faradic current to the dry skin with the metallic brush, or by allowing the cathode of the galvanic current to rest upon it for some time.
The PROGNOSIS in peripheral anæsthesia is in the main favorable, but it must, of course, depend much on the gravity of the lesion causing it, as mechanical injury, pressure, neuritis, cold, etc. Rheumatic anæsthesia, the result of exposure to cold, is in general readily recovered from. Vaso-motor anæsthesia yields in most cases without difficulty to treatment. Washerwoman's anæsthesia and allied cases are intractable, and often resist the patient and well-conducted application of remedies.
As a concrete picture of peripheral anæsthesia we will give a description of anæsthesia of the fifth nerve—the rather that in its consideration we meet with some of the most interesting and important complications occurring in connection with paralysis of sensitive nerves. The fifth nerve may have either of its three branches separately affected, giving rise to anæsthesia limited to the distribution of that branch, or all of its fibres may be simultaneously involved, giving rise to complete anæsthesia of the nerve. In the latter case the lesion of the nerve in all likelihood exists at some point of its course between the apparent origin from the pons and the ganglion of Gasser, which rests upon the apex of the petrous portion of the temporal bone. Beyond this point the nerve divides into its three branches. Amongst the causes of trigeminal anæsthesia are injuries, tumors, syphilitic thickening of the dura mater, neuritis, etc., affecting the nerve within the cranial cavity. In complete anæsthesia of the fifth nerve the parts implicated are the skin of the forehead to the vertex, the nose, the lips, and chin up to the median line, the cheek and temporal region, including the anterior portion of the ear, the conjunctiva, the mucous membrane of the nose, the mucous membrane of the mouth, and partly of the fauces of the same side. The tongue is deprived not only of common sensation on the affected side in its anterior two-thirds, but the sense of taste is also lost over the same region, by reason that the fibres of the chorda tympani, the nerve of taste for this region of the tongue, are derived from the fifth nerve. If the whole thickness of the nerve-trunk is involved, including the small motor root, there is, in connection with the anæsthesia, paralysis of the muscles of mastication on the side affected, which may be distinguished by the want of hardening of the masseter when the jaws are forcibly brought together, and by the thrusting of the chin over to the paralyzed side when the mouth is widely opened, caused by the want of action of the external pterygoid muscle, which allows the condyle on the paralyzed side to remain in the glenoid fossa, while the condyle of the opposite side is pulled forward upon the articular eminence by the sound pterygoid. The face is of a dusky or livid color, and cooler than natural. Ulcers of a stubborn character in the mucous membrane of the cheek may be caused by the patient unconsciously biting the insensitive parts. An inflammation of the conjunctiva is frequently set up, which may extend to the cornea, causing ulceration, perforation, panophthalmitis, and destruction of the eye (ophthalmia neuro-paralytica). This has been regarded by some as caused by trophic changes in the tissues, the direct result of irritation or destruction of trophic fibres connected with the ganglion of Gasser. Experiments made upon animals, however, seem to show that the inflammation of the eye depends upon the irritation caused by the intrusion of foreign bodies, which, owing to the loss of sensation, are not appreciated, and which from loss of reflex action are not removed by winking nor washed away by an increased lachrymal secretion, as in the healthy eye. It may be that although the latter is the true explanation of the origin of the inflammation, nevertheless the tissues may have lost their normal power of resistance to its invasion by reason of nutritive changes consequent upon the lesion of trophic fibres running in the trunk of the nerve. The reflexes ordinarily induced by irritation of the parts in their normal state are lost. Irritation of the conjunctiva causes no winking of the lids nor secretion of tears, and titillation of the nostrils no movements of the muscles of the face nor mucous or lachrymal secretion. The movements of the face are less lively on the affected side, not on account of paralysis of the muscles, but from the loss of that constant play of reflex activity in them which takes place in the normal condition. The loss of the reflexes distinguishes peripheral trigeminal anæsthesia from that of cerebral origin, in which they may still be excited by irritating the anæsthesic surfaces. In trigeminal anæsthesia, which sometimes occurs from the effect of cold upon the surface of the face, the mucous surfaces are not affected.
The SYMPTOMS and DIAGNOSIS of peripheral paralysis having been already given under the heads of Injuries of Nerves and Neuritis, a consideration of the distribution of any motor nerve will enable us to anticipate the distinguishing features of the paralysis dependent upon it. With each the picture will be modified according to the position of the muscles paralyzed and the motor functions destroyed. It now remains to give the symptoms, diagnosis, and treatment of the paralysis of an individual motor nerve, which may serve as an example and paradigm, in the consideration of which points of interest and instruction may be touched upon applicable to all other cases.