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.
_Lesions._ In meningeal bleeding the clot is found outside the dura, or
between the dura and arachnoid which may or may not be ruptured. A clot
on the pia mater may press seriously on the cord or may cause rupture of
the arachnoid. In hemorrhage of the cord, the effusion usually begins in
the gray matter, though it may extend far into the white. It may be
circumscribed to half an inch in diameter or affect almost the entire
length of the cord. The cord may be distinctly enlarged at the point of
effusion, and in exceptional cases the blood may have broken through to
the membranes. If the patient survives, absorption and degenerations of
the cord are inevitable.
_Symptoms._ In both forms there is a sudden attack, with stiffness or
paralysis of given muscles and without hyperthermia. Rigidity and spasms
of the muscles are more characteristic of meningeal hemorrhage, and
early paralysis of the spinal. An early hyperæsthesia is also most
significant of an effusion in the cord. Rapid muscular atrophy is also
characteristic of this. The two conditions resemble meningitis and
myelitis but come on much more suddenly and are unattended by fever.
_Treatment._ Such cases are not hopeful. Cold to the affected part of
the spine, keeping the patient in slings to solicit the good effect of
gravitation, and giving ergot or lead acetate internally are among the
first indications. Later, the treatment would be practically the same as
for meningitis or myelitis. In case of complete paralysis from the
sudden formation of a large clot, it has even been advised to cut down
on the seat of the injury and evacuate the blood, using antiseptic
precautions.