Treatment. When once established, the disease has not been successfully treated. Nerve tonics are indicated.
NEURITIS. PERINEURITIS.
Definition. Causes: traumas, poke, stanchions, collar, yoke, interfering, neurectomy, fractures, tumors, callus, rheumatism, gout, violent overdistension. Lesions: nerve sheath red, swollen, exudate, leucocytes in excess, fibroid thickening, nerve atrophy, degeneration, axis granular, myelin in oily globules, peripheral extension. Muscular degeneration and atrophy. Symptoms: tenderness, swelling, muscular atony, wasting, spasms, twitching, decreased excitability, paralysis, in section swelling on proximal end. Prognosis: disability for weeks, months or year; response to electric current, operability of tumors, curability of rheumatism or gout, hopeful conditions; long standing degeneration, etc., unpromising. Treatment: rest, soothe, anodynes, splint with soft pad, essential oils, lead and opium lotion, ice, snow; derivatives; laxatives; diuretics, anti-rheumatics, Faradisation.
Definition. Inflammation of a nerve leading to paralysis of the parts to which it is distributed.
Causes. Traumatism is the most common factor. Among the common examples are injury of the seventh nerve above the angle of the lower jaw, by a poke worn in pasture by the horse, or by stanchions in the cow. Hogs may suffer from blows of the triangular neck gear worn to prevent them from breaking through fences. Blows by the yoke, incised and contused wounds implicating the nerve, such as neurectomy, and the blows received in interfering, and compression by tumors or bony growths, are familiar examples. Fractures with displacement, notably those of the sacrum and proximal end of the coccyx with caudal paralysis, are not uncommon. In fractures of the limbs the pressure upon or wounding of a nerve. Again, the callus on the seat of fracture may induce neuritis by pressure, as may also the projection of the end of a bone in luxation. Rheumatism affecting the nerve sheaths and, in birds and swine, gout, are additional factors. Violent overdistension, and even chronic muscular spasm, are quoted as causes.
Lesions. The early changes are mainly in the connective tissue sheath, which becomes hyperæmic, red and swollen, with a gelatinoid exudate and a great multiplication of leucocytes. Later, the interfibrillar connective tissue is involved and the nervous substance proper undergoes hyperæmia and degeneration. The axis cylinder undergoes granular degeneration and the myelin breaks up into oil-like globules. The lesions are at first limited in extent, though there may be more than one focus, and the resulting degeneration of the nervous filaments advances toward the periphery in accordance with Waller’s law by which disease changes proceed rapidly in parts cut off from their trophic cells.
The muscles supplied by the inflamed nerves also rapidly degenerate. The fibres shrink in size, and lose their striated appearance, becoming distinctly granular, and pale. Round cells are formed in excess in the sarcolemma and muscular fibre, and if the morbid condition persists there is fibroid degeneration, cirrhosis and contraction.
Symptoms. In the absence of the subjective element of pain, which is the most constant symptom in man, we must rely mainly on the exquisite tenderness on pressure along the line of the nerve, but localized at some particular point, on the swelling at such tender point and on the loss of muscular power or even of sensation in the tissues corresponding to its peripheral distribution. The muscles may be hypersensitive and are usually flaccid if not from actual paralysis, still from the pain which attends on their contraction. In some cases they are the seat of clonic spasms or twitching. Under a current of electricity they show a decreased irritability which bears a direct relation to the grade of degeneration which has occurred in the nerve fibres. In cases of deep-seated neuritis paralysis may be the only appreciable symptom. In traumatic injuries like bruises of the seventh nerve or fracture of the sacrum the local swelling and tenderness are marked initial symptoms, upon which supervene the paralysis and atrophy of the muscles cut off from full innervation. In neurectomy the tender swelling in the stump which is still in connection with the nerve centre may amount to a distinct neuroma, while the peripheral and detached portion of the nerve steadily loses its irritability as shown by electric stimulus.
Prognosis. This will depend on the nature of the lesion. A single transverse section of a nerve, without loss of substance may be repaired in a few months, while with loss or degeneration of a considerable part of its substance it may maintain a paralysis for years or even permanently. Lesions due to slight bruises may recover in a few weeks, while the more severe ones will persist for months or years. The response to electric stimulus distal of the lesion, is a guarantee of the absence of degeneration and a feature hopeful of recovery. Pressure by bony displacement or neoplasia must be done away with as the first condition of improvement in such cases. Rheumatic and gouty cases will persist until these constitutional infirmities are corrected.
If the neuritis and paralysis have lasted for any length of time, the degeneration of the muscles will keep up a degree of muscular weakness (and if in the limbs lameness) after the repair of the nerve has been completed.