Lesions. Thirteen months after the commencement of the attack this horse was destroyed and the cord was found to be profoundly altered by fibroid degeneration of the neuroglia and absorption of the nerve elements (cells and fibres), the lesions affecting different portions of the gray horns, and the columns—superior, lateral and inferior. The affected portion of the cord usually shows in man a grayish, opaque or translucent appearance, with in some cases a shrunken aspect and undue firmness of texture, with at points, centres of softening. If hardened, the sclerosed sections take the carmine stain deeply, but the osmic acid or hæmatoxylin stain very slightly, contrary to what holds in health. In recent cases there is only slight thickening of the neuroglia, but when the disease is advanced the trabeculæ are thick, dense, and firm, and the nerve fibres have largely disappeared. The coats of the blood vessels adjacent to the sclerosis are thickened and their lumen is narrowed. Thickening of the meninges is not uncommon, either confined to those covering the diseased portion of the cord or extending completely around it. Atrophy of the nerve roots is often appreciable by the naked eye.
Diagnosis. This depends largely on the fact that the condition follows an acute attack of myelitis, on the supervention of muscular weakness and lack of muscular control, whenever the animal is exercised to fatigue, the morbid symptoms subsiding promptly when he is allowed to rest, the aggravation of these symptoms when the patient is blindfolded and a gradual though slow advance of the symptoms with the lapse of time. From arteritis and embolism it is to be distinguished by the absence of the local symptoms of pain and tenderness, and by the absence of pulsation in the same artery distal of the obstruction and of improvement by the lapse of time or a run at grass.
Treatment: Unless in the very early stages even a partial recovery is not to be looked for. By a run at grass or by gentle well regulated exercise the impaired nerves and muscles may be educated to a better control for a limited period but the progress of the disease is not really arrested and the final issue is likely to be ruinous. Even in man, where 90 per cent. of the cases are connected with syphilis, the fibroid hyperplasia (sclerosis) is not remedied asgummata are, by mercury and iodides. In the soliped, where no such specific disease can be charged, the repair of the structural changes is no more hopeful. The many different methods of treatment in man,—electricity, blisters, firing, stretching of the spine, stretching, of the sciatic and crural nerves,—though inducing transient improvement in many cases, produce no real permanent benefit, and are to be remanded to the region of psychic inferences which have little or no place in the therapeutics of the lower animals. Strychnia, veratrin and other spinal stimulants are of little permanent value. A general hygienic and corroborative treatment may be used with the view of retarding the progress of the disease rather than of curing it. Open air exercise, sunshine, succulent pasturage, an ample supply of pure water, and active grooming are valuable. Nourishing food is all important. Lecithin or the hypodermic injection of spermin or other rich albuminous animal product is useful. A course of bicarbonate of soda and carbonate of iron with or without bitters may be tried. When the animal must be kept on dry winter food, he should have free access to common salt and water. This favors at once absorption, assimilation, and elimination, and by fostering nutrition and the removal of waste matters, it contributes to keep the disease in abeyance. Phosphoric acid and the various phosphates have been largely used and largely rejected, their main value being in the tonic effect on the spinal centres. Trasbot especially recommends the neutral gelatinoid phosphate of lime as having proved especially valuable in his hands. He gave from 1 grain upward to dogs twice a day.
ARTERITIS (THROMBOSIS, EMBOLISM) OF THE SPINAL CORD AND MEMBRANES.
Conditions of spinal circulation favorable to embolism and microbian invasion. Slow currents. Blood stasis. Free anastomosis a compensation. Symptoms. Treatment.
Facts are wanting with regard to these lesions in the domestic animals, but anatomical, physiological and pathological consideration are strongly suggestive of their occurrence. The vascular network of the spinal cord favors a tardy circulation, and this in turn is favorable to the arrest of solid bodies and the delay, proliferation and colonization of microbes. The median spinal artery receives a supply of blood by two trunks, right and left, entering by the intervertebral foramina at each intervertebral articulation. It has not, therefore, one continuous, equable, onward flow, but rather numerous independent currents corresponding to the entering vessels, and with intervening eddies or areas of comparative stagnation. The nervous material of the cord admits no large arteries but only capillary trunks which anastomose freely in its substance. This would seem to entail a sluggish flow, which would favor microbian arrest and colonization, even if the small size of the vessels serves to shut out clots of any material size. Finally the abundant venous plexus, and especially the two lateral venous sinuses, communicating freely with each other and, through each intervertebral foramen, with the extra spinal veins determine a similar tardy flow that should be favorable to morbid processes. If we pass back of these vessels, we find the posterior aorta to be at once the largest and the most direct channel for the entrance of emboli coming from the left heart or lungs. This danger is counteracted in greater part by the fact that the greater part of this blood passes into the large vessels which supply the liver, spleen, kidneys, stomach, bowels, and hind limbs, and while embolism is well known in these parts it has not been demonstrated as yet in the spinal cord. The toxins produced in infectious diseases and circulated in the blood can often lead to destruction of the endothelium, and inflammation of the deeper structures. In this way any circulating microbes find a ready infection atrium. Hektoen seems to have demonstrated this in the case of tubercular meningitis. By pressure of the neoplasm on the vessel or by fibroid thickening and contraction of the walls of the vessel, the subsidiary cord is denied its full supply, and degeneration of the nervous substance is invited. In the human subject degeneration of the cord has been shown to follow the line of such diseased arteries. Thrombosis follows in every case in which the serous coat is involved, and embolism can easily occur from clots small enough to enter the capillary vessels. Lamy’s experiment of blocking the small arteries with inert powder, shows that this will give rise to foci of hemorrhagic softening, which commence in the gray substance. The blocking, however, must be multiple to produce any material effect, as the free anastomosis of the spinal capillaries otherwise secures an abundant blood supply to adjacent parts. In case of an infective embolism the disease will advance even if the obstruction is single.
The general symptoms of these conditions would depend on the exact seat of the lesion, and treatment would have to proceed on general principles, the object being to check the inflammatory conditions, and trust to the vis medecatrix naturæ in connection with rest and good hygienic conditions.
HEMORRHAGES INTO THE SPINAL MEMBRANES.
Meningeal Spinal Apoplexy. Hæmatorrachis. Hemorrhage into the Spinal Cord. Spinal Apoplexy. Hæmatomyelia.
Definition. Causes: violent exertion, blows, falls, morbid blood, fractures, caries, tumors, tubercle, aneurisms. Lesions: Clot between or outside membranes in meningeal hæmorrhage, in gray matter and even in white in myelon bleeding. Cord bulges. If survives, nervous matter absorbed. Symptoms: Sudden stiffness or palsy of given areas; spasms more common in meningeal extravasation. Rapid muscular wasting. No fever at first. Treatment: cold to part; slings; atropia, ergot, lead acetate. Later as for myelitis. Large clot may warrant surgical interference.
In the first of these forms the bleeding takes place between the arachnoid and the two contiguous membranes—pia and dura, or outside the dura. In the second it takes place into the substance of the cord though it may encroach on the pia mater. Both conditions have been attributed to violent muscular efforts or contractions as in draught, racing, fighting, leaping, tetanic convulsions, also to blows on the back, or falls from a height. Morbid states of the blood in which there is a hemorrhagic tendency (scurvy, purpura, hæmophilia, anthrax) may be contributory causes. Spinal fractures, aneurisms, caries, tumors, and tubercle may be additional causes.