DISEASES AND INJURIES OF NERVES.
Inflammation of Nerves flammation in any part of the body may attack the nerves distributed in or passing through that part. That is to say, the nerves may simply partake of inflammation occurring in their neighbourhood, and may suffer as all the other tissues of the part do, adding enormously to the pain and general disturbance of the local inflammation. Similarly nerves may be attacked by disease just as other tissues are. Thus cancer, tubercle, syphilis may invade nerves as they do other tissues. But nerves also may be picked out, so to speak, by disease, the nerve affection being the main or the only manifestation of the disease.
Inflammation affecting nerves is a process similar to inflammation elsewhere, attended by increased blood-supply, congestion, and so on, and it may subside in time for the nerve to recover fully, or suppuration may occur, or the inflammatory material formed in and about the nerve may so compress the nerve as wholly or partially to destroy it, causing it to undergo degeneration in whole or in part.
The symptoms produced by these changes will vary according to the duty the nerve per forms. If it is a nerve going to a muscle, the muscle will be weakened or paralysed for a time and will undergo wasting or atrophy. If the nerve recovers in time, all this may be recovered from; but if the nerve is destroyed wholly or partially, the muscle will be correspondingly permanently impaired. Thus there is produced a local paralysis. If the nerve is a large trunk, supplying a large number of muscles, then a corresponding number of muscles will be in volved and a whole limb may suffer, more or less, and temporarily or permanently.
If the nerve is a sensory nerve, then the chief manifestation will be pain or some other disturbance of sensation or loss of sensation, greater or less, temporarily or permanently, ac cording to the extent and nature of the nerve affection. Moreover, as sensory nerves not only confer sensibility ou the skin, but also preside over the nutrition of the skin, the nourishment of the part of the skin supplied by the affected nerve will be impaired, and sores or sloughs will form.
If the nerve is a mixed nerve, partly motor and partly sensory, then the disturbances due to its disease will involve the muscles and the skin, so far as supplied by it.
Nerves, we have seen (p. 131), regulate blood supply, control the activity of glands, main tain the nutrition of joints, and so, according to the nerves affected, there may be manifesta tions of disturbed circulation, irregularities of secretion, affections of joints, and so on.
The causes of such conditions are too varied to permit of their detailed consideration in such a work as this. Some of them may be merely noted. Injury is, of course, a very •fre quent cause. The neuritis in such a case would be confined to the nerve injured. Exposure to cold is another cause. For instance, the par alysis of one side of the face due to a draught from an open window playing on one side of the face is the result of a neuritis of the nerve of the face, the seventh cranial, or the facial nerve (p. 152).
Rheumatism and gout are very common causes, or, to put it in other words, the poison circulating in the blood, which is the cause of rheumatism or gout, while it attacks the joints in some persons, may in others produce an inflammation of nerves. In such a case one nerve might be attacked at one time and an other nerve at another time, or several or many nerves more or less simultaneously. One might thus have what is called a multiple neuritis, of gouty or rheumatic origin, in which treatment would not be directed so much to the particular nerve or nerves involved, but to the gouty of rheumatic state of body.
In the same way the nerve inflammation or neuritis might be a tubercular or a syphilitic one; and it is a common complication of dia betes. The poison of many infectious diseases shows a marked tendency to produce nerve inflammations in sore people. Diphtheria is notably so, and thus is produced diphtheritic paralysis. Influenza is also notorious in this way, and doubtless some at least of the severe pains suffered in influenza attacks are due to nerve inflammation. But similar affections of nerves may occur in erysipelas, typhoid fever, and others of the infections. A very remarkable illustration of this is a disease, first described in Japan, where it is called Kakke, but also occurring iu the islands of the Pacific, in the Philippines, Borneo, and the Dutch islands of the Pacific, where it is called Beriberi. It is au epidemic disease, and is an infectious multiple neuritis, in which, with fever, there is weight and weakness of the legs, some loss of power of movement and of sensation, which, in severe cases, goes on to paralysis, extending from the .legs over the whole body, accompanied by severe pains. In these severe cases the patient becomes extremely helpless, emaciated, and dies of ex haustion, and it may be a very fatal disease.