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.
Legal Aspect of Chronic Hydrocephalus.
To claim relief in case a horse affected in this way is sold as sound,
the seller must be notified at an early date. In the different countries
of Europe a limit is set after which such notification will have no
legal value. The seller must be notified, in France in 9 days, in Saxony
in 15 days, in Bavaria, Wurtenberg and Baden in 21 days, in Hesse and
Prussia in 28 days, and in Austria in 30 days.
_Diagnosis._ The veterinarian called to act as expert in such cases must
examine the suspected animal along the different lines in which the
cerebral aberration is manifested in the disease. He will see the animal
standing quietly in the stall apart from all sources of excitement. See
if there is a defect in the breadth of the cranium, or a deflection
backward of this region from the straight line of the front of the face,
together with a heavy clumsy head. Is the head pendent, resting on the
manger, with dull eye, drooping lids, lack of expression, loose hanging
lower lip? Does he hold morsels unchewed projecting from the mouth or
over the tongue, or in the cheek? Does he plunge both mouth and nose in
the water to drink, and masticate meanwhile? Are his legs found crossed
or in abnormal positions, and if put in such positions, does he fail to
rectify them at once? Is the head left in an abnormal flexed, depressed
or lateral position if placed in it? Does the subject find it difficult
or impossible to back? Does he pay the customary attention to the going
or coming of other horses, to feeding, etc.?
If no distinct symptoms are found he should then be examined under other
conditions. In taking out of the stable how does he turn in the stall or
back out of it, and in what way does he approach the door, clumsily or
with difficulty? When moved in a circle, does he sway or stagger? Can he
back when mounted or attached to a heavy carriage? Can he execute all
these movements satisfactorily after the respiration and circulation
have been excited by walking, trotting or galloping in hand or
otherwise? In case of difficulty in backing, in the absence of the other
diagnostic symptoms, he must see that this does not arise from other
causes. Some untrained horses have not been taught to back and cannot be
made to do so at once. Some refuse to back from indocility or
stubbornness, but can perform the act if induced in other ways, as in
having a narrow stall. Sometimes a sore mouth, from a hard bit may make
a horse nervous and obstinate so that he will seek to escape in any
other way rather than by backing under steady pressure of the bit.
Sometimes he will back all right under a halter. In all such cases of
simple obstinacy or fear of pain, the absence of the other symptoms is
strongly suggestive. If the horse has a well-developed cranium, a full
bright, alert eye, firmness of lips, intelligent expression, readiness
to appreciate and respond to all noises, words, touches or other causes
of excitement, plenty of fire and spirit, and an absence of any apathy,
dulness, awkwardness of movement or position of the limbs, or of any
other sign of failing nervous power he may be considered free from this
affection, even if he refuses to back in a docile manner. In other cases
there is a distinct physical incapacity quite apart from any brain
disorder. Sprains or anchylosis of the back or loins or anchylosis or
painful arthritis of the hocks, may hinder backing.
The diagnosis from encephalitis and other inflammatory affections
associated with stupor, rests on the absence of hyperthermia, of the
congestion of the orbital and nasal mucosæ, of the heat of the head and
of the paroxysmal attacks of excitement which characterize these
diseases.