CHRONIC HYDROCEPHALUS. DROPSY OF THE VENTRICLES. IMMOBILITY.
Horse especially suffers. Enzootic in given Alpine Valleys, along Rhone, in Mississippi Valley and bottom lands. Acclimatizing fever. Old, lymphatic, large heads, narrow foreheads predisposed. Geldings. Causes, heredity, cerebral and meningeal congestion, cranial traumas, venous obstruction, tumors, false membranes, fodder or water poisoning, overwork, insolation, prolonged moist heat, hepatic, gastric, and pulmonary disorders. Symptoms: form of head, stupid expression, irresponsive ears, pendent lips, sluggish movements, crossed legs, slow mastication, dips face in water, intractable by halter or rein, unable to back with rider, or wagon, drags back fore limbs, worst in hot damp weather, in sunshine, or after work, or with full stomach. Paroxysms of excitement. Lesions: excess of arachnoid, subarachnoid or ventricular fluid, atrophy of ganglia and convolutions, ependyma thick, opaque, sclerosis, brain anæmic. Tumors, nature. Experimental cases. Prognosis, incurable, better in cool season. In cattle, sheep, swine and dogs. Treatment: derivatives, nerve stimulants (nux), puncture, pilocarpin, purgatives, Jurisprudence. Notify seller in 9 days (France), 15 (Bavaria), 21 (Wurtenberg, Baden), 28 (Hesse, Prussia), 30 (Austria). Examination by expert.
Dropsy of the ventricles is common in the horse in certain countries and districts, yet even there it is uncommon in cattle, sheep, swine and dogs, save as a congenital affection. It is reported as enzootic in some Alpine valleys and along the Rhone, attacking especially the mares and immature horses so that breeding becomes impossible. Mauener who reports this says that in the same localities encephalic diseases are more common in man. In America it appears to be most frequent in the rich bottom lands of the Mississippi valley and of the Southern States. Northern horses taken to the Gulf States though they may not suffer to this extent, are liable in the first year to show weakness, debility, and lack of vigor which is spoken of as the acclimatizing fever. Elsewhere the affection is one of the old horse in which the vital powers begin to fail. Common breeds of horses with lymphatic temperament, large head and narrow forehead have been found to be especially predisposed. Geldings are said to be most liable on account of the arrested development of the brain, but with the great preponderance of geldings among work horses, it is dangerous to generalize too far.
Causes. Acute encephalitis may lapse into the chronic form and then assumes the symptoms of this disease. Cases that come on slowly and imperceptibly appear at times to be hereditary, as might be expected from the fact that it usually goes with a lymphatic temperament. The conditions which cause cerebral or meningeal hyperæmia in chronic form conduce to the affection. Injuries to the cranial vault from traumatism or disease are infrequent causes. Renault records a case associated with two bony tumors, each as large as an egg, projecting inward from the frontal bone and which had produced extensive absorption of the convolutions and increase of the cerebro spinal fluid. In a case of my own with an abscess in the diplöe above the frontal sinus, and pressing inward on the brain a similar condition existed. In other cases Renault noticed that the cerebro spinal fluid was largely in excess.
Much more commonly, however, the accumulation of liquid takes place in the ventricles, and is associated with different causes: as tumors or false membranes near the base of the brain pressing on the veins returning blood from the ependyma, tumors in the ventricles (cholesteatomata, etc., of the ependyma or choroid plexus) obstructing the circulation or giving rise to local hyperæmia and chronic congestions from the other causes such as faulty conditions of fodders, or water, exposure to undue heat, overwork, etc. The enzootic prevalence of the disease in certain localities, (Alps, Rhone Valley, bottom lands) would suggest that local conditions in food or water are factors, though we cannot as yet fully explain the mode of causation. In the same way we must recognize the influence of hepatic and gastric disorders, which arise from such faulty regimen and affect the brain by nervous sympathy and by the action of toxic elements thrown into the circulation. Then again we must take sufficient account of the congestions resulting from obstructions in the lesser circulation, disease of the lungs, and of the right heart, and compression of the jugulars by a tight or badly fitting collar, or compulsory curving of the neck as set forth under vertigo and cerebral congestion.
Symptoms. Among the symptoms must be recognized the conformation with which it is usually found associated. The predisposed animals are usually low bred, common horses, with narrowness of the cranium and space between the ears and with a retreating of the head from the orbits to the poll. Other horses suffer but the majority are of this conformation, and thus the disease acquires a hereditary basis.
The expression of the face is characteristic. The eye is dull, often sunken, lacking in vivacity and life, the eyelids are semi-closed, the ears do not prick up to sounds, the muscles of the face are relaxed, so that the lips hang flaccid, and the nostrils fail to dilate freely and rhythmically. The animal is apparently unconscious of all that goes on around him, and is not aroused by the entry or exit of men or horses, by voice or slap, by food or water. His head is probably dropped and resting in the manger, and he raises it sluggishly when compelled; when moved from side to side of the stall his legs may retain a position turned outward or crossed one over the other; if energetically roused he wakes up slowly, and almost immediately relapses into his former lethargy, without accomplishing what was called for. When left with legs crossed he often remains so until wearied by the constrained position, or in danger of falling from loss of balance. Not only the legs but the head will retain for a time an abnormal position given to it,—bent, dropped, turned to one side or the other.
This same lethargy extends even to mastication, which is usually performed slowly and indifferently, and is often interrupted in the middle of the trituration of a morsel which remains in the cheek, on the tongue, or between the teeth, and perhaps hanging out of the mouth. Hence the horseman’s expression, he smokes his pipe.
His mode of drinking is no less singular. Usually the lower part of the face is dropped deeply into the water, and he will only withdraw it when it becomes necessary to breathe. He may continue to masticate while drinking.
When walked or trotted he may move a short distance all right; he may even hasten his progress for a short distance without refusing meanwhile to respond to the rein, then he may stop and for a short time longer resist all efforts with voice, whip, or spur to start him anew. In other cases he will turn to one side, getting into ditches or fences by an apparently involuntary action and in defiance of whip or reins.
One of the most striking features of the disorder is the difficulty of backing. In some cases he will back a few steps and then prove unable to back farther; in others he will show it best when heated with a journey; in other cases still he will back well enough under his own weight, but prove utterly unequal to the act if a heavy man is placed on his back, or if hitched to a loaded wagon. In backing with or without a rider the horse, pulled back by the reins, inclines backward with his hind limbs extended forward beneath the abdomen, his forefeet extended in front, and his back arched; he extends his head or turns it to one side, and when the change in the centre of gravity endangers his equilibrium, he draws back his forefeet without lifting them, each making a groove in the ground, and at the same time he makes a disorderly motion of the hind limbs to one side to restore the balance. In default of this he may drop his quarter on the ground and perform a back somersault on his rider. Even when he succeeds in balancing himself after dragging the forefeet back, the difficulty of further backing is rather increased, as the nervous irritability is enhanced by a continuance of the excitement.
When hitched in a carriage the phenomena are virtually the same; when backed he extends or flexes the head, inclines the body backward, and after a time loses his equilibrium, sometimes executes a few disorderly steps backward, or throws himself violently to one side, or turns over backward in the shafts.
The symptoms are always worse during hot, damp weather, and when the animals are exposed to the full glare of the sun. The milder cases can be worked without great inconvenience in winter, while they become utterly useless in summer.
Active exertion and increased rapidity of the circulation has a similarly injurious effect. After a period of rest nothing amiss may be noticed, while after a period of work in the sunshine the symptoms become well marked and the difficulty of backing pronounced. Plethora or full feeding aggravates, while spare, laxative diet, laxatives, rest or bleeding relieves.
The affection may become complicated by more active inflammatory action leading to paroxysms resembling those of meningo-encephalitis;—pushing against the wall, rearing up with the fore feet in the manger, acting as if walking or trotting, etc. In other cases the paroxysms resemble those of vertigo; the animal plunging forward, starting to one side, or rearing up and falling back.
Lesions. The pathological anatomy of this disease is that of chronic hydrocephalus. Renault records cases in which the subarachnoid and arachnoid fluids were under the normal while the fluid in the ventricles was increased to a marked extent. This accumulation is often so great that the whole of the surrounding nervous matter is greatly attenuated, the convolutions of the cerebral hemispheres are flattened so that the sulci are all but effaced, the water may shine through at points and even bulge after the manner of a hernia, the ganglia in the ventricle (corpus striatum, optic thalamus, hippocampus) are flattened and atrophied, the base of the cerebrum is thinned and bulges downward, and the olfactory lobes may have their internal cavity greatly distended so that they look like little bladders of fluid. The ependyma may have lost its normal thinness and translucency, having become thick and opaque, and sometimes its surface is granular and rough. The choroid plexus is congested and swollen with infiltration. The brain tissue adjacent is firmly adherent and there is a hyperplasia of its connective tissue constituting a veritable sclerosis. At some points, however, the compressed nervous tissue has undergone degeneration and softening. As might be expected from the pressure of the liquid, anæmia of the brain tissue is a marked feature of the morbid condition.
Other conditions have at times been found in chronic hydrocephalus.
Renault found two long tumors each as large as a hen’s egg projecting from the dura mater into the cerebral hemisphere. In other cases there have been fibrous thickening of the dura mater, exudations on the pia mater, and false membranes on the arachnoid (Röll). Chabert and more recent writers have observed cysts and tumors of the choroid plexus in such cases, but these have been met with not unfrequently in the entire absence of the characteristic symptoms of this disease.
Nature. The affection before us is evidently one in which the majority of the higher brain functions are profoundly depressed or debilitated, and this is accounted for by the accumulating intraventricular liquid pressing on the ganglionic centres in the cerebral hemispheres, and in the floor of the lateral and third ventricles.
Experimentally an approximate loss of sensation, intelligence, spontaneity, will, and muscular power is produced in birds or mammals deprived of their cerebral hemispheres. Colin’s heifer, which had been thus mutilated, would lie in torpor, and though it could be made to get up and walk, it struck its head heedlessly against the wall, and retained in its mouth unchewed, the food that had been placed there. He says of such cases: “they live a long time, move automatically, respire, digest, but they lose, with the sensations, memory, judgment, will, and the most vital instincts of their kind.”
In the dropsy of the ventricles the attenuation and atrophy of the cerebral convolutions produce symptoms which approximate closely to those resulting from their experimental ablation, so that one may fairly attribute the general symptoms in the two cases to the loss of their function. Many of the attendant symptoms, and especially the aberration of smell, sight, hearing and taste, may be referred to the concomitant injuries of the basal ganglia of the brain.
We need not seek in one general answer to resolve the question whether the dropsy or inflammation is the initial lesion. For our present purpose it must suffice, that dropsy with anæmia and atrophy of the cerebral convolutions and basal ganglia produce the symptoms of immobility.
At the same time it is only logical to conclude that any morbid condition of the cerebral circulation or of the brain or membranes which leads to a corresponding amount of ventricular effusion, or atrophy or destruction of the nerve centres already designated, will produce the symptoms characteristic of this disease. Thus the different forms of meningitis, traumatic injuries to the cranium, chronic encephalitis, cerebral softening or degeneration, sclerosis, neoplasms of all kinds affecting the brain (cysts, cholesteatoma, psammoma, melanoma, etc.), and parasites may occasion this disease.
Prognosis. The disease is essentially incurable. It may last for years with little change except the winter improvement, but it rarely subsides permanently. It is only in those cases in which the symptoms have been determined by a transient or removable cause, as a moderate exudation or a parasite with a short term of life that a favorable result may be looked for. Usually the improvements seen in cool seasons or stables, under good hygiene, are not recoveries but temporary amelioration only.
Symptoms in other animals. Corresponding conditions produce similar symptoms in cattle, sheep, swine and dogs, but the disease receives less attention in these animals because they are not called on for steady work. The animals are lazy, dull, insensible to excitement, stupid, show a lack of muscular power and control, stagger or move disorderly and show tympanies or other indications of indigestion.
Treatment. Majendie and others had a few apparent recoveries after violent counter-irritation over the spinal cord (cervical and dorsal). Coculet and Lafosse claimed recoveries from the prolonged use of nux vomica in large doses (up to 5 drachms). Hayne attempted evacuation of the fluid by puncture through the perforated plate of the ethmoid bone, but had evil results from the ensuing hæmorrhage and encephalitis. Aseptic puncture through the plate of the frontal bone would be much more promising. Klemm suggested hydrochlorate of pilocarpin (15 grains), and this would promise better than any other measure to induce absorption of the liquid. The fatal drawback to this as to other measures is that it is not applied until the slow, steady pressure has caused such extensive cerebral atrophy that, even if the liquid could be removed and its reproduction prevented, the lost functions can never be restored. If the disease could be diagnosed and treated before this change of structure had taken place, the hope of recovery would be much better founded. Even in cases which make a temporary recovery during cold weather one would be warranted in using active derivatives toward the bowels and kidneys, also pilocarpin, counter-irritation to the spine and even tapping of the ventricles.