feature in supposed hemorrhage from concussion, as sudden paraplegias
of motion and sensation are found in some cases of railway spine, and,
although a number of cases terminating fatally have been examined,
there was not always hemorrhage even in the meninges.]
[Footnote 80: Until authorities shall have agreed as to what effect
the exposure of the bodily periphery to certain temperatures has on
the circulation of the cord, it would be premature to make any special
recommendations as to the temperature at which they should be kept. I
am inclined to believe that while, as is universally accepted, a
general cooling of the bodily surface tends to increase vascular
fulness in the cord, as in all other internal organs, a partial
cooling, as of the feet, produces local anæmia at the level of origin
of the nerves supplying the cooled part. Certainly, the bilateral
neural effects of unilateral cooling are in favor of this view.]
The descriptions given of the hemorrhagic foci as observed after death
strengthen the view that they were in the majority of cases of
myelitic origin. Usually, they are stated to extend up and down the
cord in the direction of least resistance—that is, in the gray
substance—resembling an ordinary apoplectic clot. But in their
neighborhood there was usually considerable softening, and, to judge
by the descriptions given, this softening differed in no wise from
that which is the characteristic feature of acute myelitis;[81] and
often the transition from a peripheral zone of white {810} softening,
through an intermediate zone of red softening, to a central compact
clot, is so gradual as to leave it unquestionable that the softening
pre-existed, and that a vessel had broken down in the midst of the
myelitic detritus. Many ancient foci of myelitis betray the
hemorrhagic complication of their initial period by the presence of
pigmented residue of the absorbed clot.
[Footnote 81: In the latest treatise on nervous diseases published in
our language (Ross, _loc. cit._, vol. ii. p. 325) the insufficient
foundation on which a whole chapter has been built up is illustrated
by the admission that the usual evidence of acute central myelitis may
be observed far beyond the limits of the hemorrhagic infiltration. If
a large area of softening in the brain were found to contain a central
or peripheral clot of blood, and histologically resembling a typical
embolic or thrombic softening, no one would be in doubt as to which of
the two was the primary lesion.]
Embolisms and embolic softenings of that part of the spinal cord which
is supplied by the small spinal vessels are so rarely observed in the
dead-house that our knowledge of their possible occurrence and
character is almost entirely the result of experimental observations
or based on analogy. The situation of these vessels, the angle at
which their supply-tubes are given off from the aorta, all act as
protectors of the cord against what is one of the chief dangers to
which the brain is exposed. No definite symptoms have been attributed
to the few doubtful cases of simple embolic occlusion of the spinal
arteries found accidentally in human subjects. Even those emboli
which, when once let loose in the circulation, are found distributed
in nearly every organ of the body, those derived from ulcerative
endocarditis and those due to the invasion of micrococci, are
comparatively rare in the cord. Leyden found multiple capillary emboli
in the spinal cord from the former cause. Small grayish white foci in
a similar distribution were found to be due to an invasion of
cocco-bacteria from a decubitus by Rovigli.[82] In this latter case an
increase of pain and muscular spasm in the history of the case of
sclerosis which was thus complicated was attributed to the parasitic
affection.
[Footnote 82: _Rivista sperimentale di Freniatria_, 1884, x. p. 227.]
Just as simple and infectious embolic lesions are frequent in the
brain and rare in the cord, so purulent inflammation or abscess is an
exceptional occurrence in spinal as compared with cerebral pathology,
and probably for the same reasons.
Simple Acute Myelitis.
SYNONYMS.—Spontane (primäre) acute Rückenmarkserweichung, Softening of
the spinal cord, Ramollissement blanc de la moelle, Myélite aiguë.
As Leyden, whose treatise[83] may be regarded as the foundation of our
knowledge on this subject, correctly avers, it is to Abercrombie and
Ollivier that we owe the determination of the existence of that acute
structural disease of the spinal cord, now termed myelitis, as an
affection independent of meningeal changes. The anatomical
descriptions given by these older writers may be accepted at the
present day as models of accurate observation by the naked eye. Their
statement that in acute myelitis the substance of the spinal cord is
softened and changed into a puriform, yellowish, diffluent mass; that
while the disorganization is sometimes more marked in the posterior,
at others in the anterior, and occasionally in the lateral half, it is
most pronounced in the axis of the cord, because the central gray
substance is the favorite starting-point {811} of the morbid
process,—requires no modification to-day. Considerable doubt existed
in the minds of the contemporaries of Ollivier and Abercrombie as to
whether this change was the result of a true inflammation; and one of
the clearest thinkers of the day, Recamier,[84] regarded myelitic
softening as a lesion peculiar to the nervous apparatus, and different
from ordinary inflammation. I believe that the most profound
investigators of the present day have not been able to rid themselves
of a similar doubt. The discovery of Gluge's so-called inflammatory
corpuscles, which was regarded as settling the question, only served
to confuse the student by the confidence with which it was urged that
they were infallible criteria of the inflammatory process. Under the
non-committal designation of granule-cells these bodies still flourish
in the annals of cerebro-spinal pathology. As we shall see, a number
of products of real disease, of artifice, and of cadaverous change
have passed and do pass muster under this name. The first substantial
progress in our knowledge of the minute processes underlying
inflammation of the spinal cord was made by Frommann and Mannkopf, but
it applied altogether to the chronic inflammatory or cirrhotic
affections of the cord. The difference between acute and chronic
myelitis is greater than is the difference between acute and chronic
inflammation in any other organ; and it must be admitted that if
Recamier is to be regarded as having erred in asserting that acute
myelitis is not a true inflammation, he is justified in so far as he
asserted many features of the process to be altogether peculiar to the
organ affected. Leyden himself attempted to throw light on the subject
by provoking myelitis experimentally in dogs. He injected Fowler's
solution into the spinal cords of three dogs, and in each instance
produced changes which he interpreted as comparable to the myelitis of
human pathology. But the inflammation thus provoked was not of the
cord-substance alone; it also involved the membranes, and the
inflammatory foci were in several instances purulent. Now, pus
never[85] forms in ordinary myelitis. An abscess of the cord never
occurs where a septic agency can be excluded. In six dogs whose spinal
cords I wounded in the dorsal and lumbar regions by aseptic methods,
and who survived from two to seven days, I never found purulent or
indeed any active inflammatory process, as that term is ordinarily
understood, but exactly such passive and necrotic or reactive changes
as occur in the acute myelitis of human pathology.
[Footnote 83: _Klinik der Rückenmarkskrankheiten_, ii. p. 115.]
[Footnote 84: Cited by Leyden.]
[Footnote 85: In the textbooks and encylopædias, without an exception,
the statement that pus may be a product of myelitis is made. This is
true of traumatic cases and of such depending on septic and zymotic
causes alone. I am unable to find a single carefully observed case of
the occurrence of pus in simple myelitis in the literature.]
Owing to the advance of clinical and anatomical knowledge made within
the past fifteen years many forms of spinal disease classed with the
inflammations have been recognized as distinct pathological entities,
no longer to be confounded with simple acute myelitis, ordinarily so
called. Special forms of acute spinal paralysis, notably acute
poliomyelitis anterior of children and the corresponding chronic
affection among adults, have become separated in this way, and are
accordingly treated of in separate parts of this volume.[86]
[Footnote 86: For other and practical reasons the traumatic and
compression forms of myelitis are also assigned a separate place.]
{812} Some dispute exists as to the propriety of making a distinction
between acute and chronic myelitis, since an acute myelitis, if the
initial attack be recovered from with life, presents a similar
condition clinically as chronic myelitis; and this quiescent or
slowly-progressing condition may extend over many years. The term
acute with reference to inflammation of the spinal cord refers only to
the active period of the disease. Just as an embolic softening of the
brain is an acute affection, but may be followed by a chronic
paralysis or aphasia, so the acute myelitic process may be followed by
a chronic paraplegia. It is improper to call the latter a chronic
myelitis. It is merely a protracted symptomatic sequel of the acute
process. The latter is distinguished from chronic myelitis both
clinically (by the rapidity of its onset) and anatomically (by the
early dissolution of nerve-elements in the focus of disease). Limited
in this sense, acute myelitis, excluding the special clinical forms
already adverted to, is rather a rare disease.
MORBID ANATOMY.—The most recognizable change noted in an acute
myelitic focus is one of consistency: the spinal substance is
softened. In some cases the softening is so slight that the observer
may doubt whether he has a pathological or cadaveric softening to deal
with, the dorsal cord, which is most apt to be the site of an acute
transverse myelitis, being precisely the part which is most apt to
show the latter change even in fairly well-preserved bodies. In
extreme cases the softening may be so intense that the cord-substance,
completely fluidified, runs out of the meningeal sac, leaving the
latter a collapsed membranous cylinder to mark the place where the
cord once was. Where the cord-substance is sufficiently firm to permit
of sections being made through it, the normal outline of the gray and
white substance is found obliterated, either presenting the appearance
as if the gray and white matter had been stirred up together or of a
more uniform color-change. The color may be either white, reddish,
yellowish, or chocolate-like. It depends upon the participation of the
blood-vessels in the change. If there be much hyperæmia, there will be
developed what is known as red softening; if there be much
extravasation and commingling of blood with the diffluent cord-tissue,
a chocolate color will mark the diseased area; and similarly one and
the same focus may present different tints in different parts
according to the age and intensity of the process and the more or less
advanced retrogressive metamorphosis of the extravasated fluid. As
already stated, the purulent form of softening or abscess does not
occur in ordinary myelitis.
There is considerable variation in the extent of the affected areas of
acute myelitis. In the typical and severe transverse form the whole
thickness of the cord may be disorganized, and the disorganization may
extend in the length of the cord, so as to involve the level of exit
of from two to five pairs of nerves. In less furibund cases the area
of absolute softening is confined to the gray substance and its
immediate neighborhood, the submeningeal white substance being but
slightly affected or escaping. Sometimes several foci of intense
softening are scattered through a short length of the cord and
connected by less severely involved areas of softening or œdema.
Leyden distinguishes three types of distribution—the transverse, the
longitudinal, and the disseminated insular or multiple form. He
includes under the {813} longitudinal type the so-called central
softening of Albert, but undoubtedly many cases of syringo-myelia have
passed under this designation. The submeningeal form of softening
which, with Ollivier, he states to occur in association with spinal
meningitis, must be a very rare affection, as it is difficult to find
a well-established case recorded. The longitudinal form shows the same
predilection for the gray substance which the acute myelitic process
generally does, but I have seen a finely demarcated fascicular
myelitis limited to the lateral column in a paretic negro. In this
case the pyramid tract and the contiguous area in front of it were so
intensely softened that for a length of twelve centimeters a hollow
canal ran through the cord in the place previously occupied by the
diseased substance. In recent cases of myelitis the diseased area is
usually found surrounded by a transition zone in which, the morbid
change gradually becoming less intense, the consistency is firmer, and
which merges into that of the normal cord. In cases where death occurs
after a few weeks a more abrupt demarcation is usually found; this is
due to the reactive changes occurring in the neighborhood. The
connective tissue becomes firmer, and thus the softening centre
becomes surrounded by a sclerosing capsule. Ultimately, the centre
undergoes complete disintegration and absorption, and a cavity is left
behind filled with a clear fluid; in short, a cyst surrounded by a
firm capsule represents the residua of disease. In cases where the
softening at the centre of the focus does not proceed so rapidly nor
reach so high a degree as to result in liquefaction, the less
vulnerable elements, the blood-vessels and supporting tissues, survive
the death of the ganglionic and conducting substance; the connective
elements hypertrophy, and thus a firm sclerotic patch is formed,
indicating the location of the previously softened field.
It seems to be generally admitted, with Hayem, that the blood found
exuded in the hemorrhagic form of myelitis does not necessarily
indicate an active determination, but is rather, like some forms of
so-called red softening of the brain, the result of capillary rupture
or necrosis in the midst of the disintegrated tissue, now rendered
incapable of supporting the vessels. The existence of a purely white
form of myelitic softening shows that a textural change is the primary
occurrence, and that the participation of hyperæmia or congestion is
not an essential feature of myelitis. The assumption of an initial
inflammatory congestion is made rather on theoretical grounds than on
the basis of observation. It is simply incredible that, as Ross[87]
claims, white softening should be a third stage, preceded by red and
yellow softening as a first and a second stage! How the extravasated
blood, which pathologists generally allow to leave long-lasting
traces, manages to disappear, and how blood-vessels in the midst of
necrotic or œdematous surroundings suddenly acquire such contractile
energy as to produce a total emptying of their contents while the
perishable nerve-elements remain behind, are problems which should be
solved before attempting to assign to a condition which is often found
to be a primary phase of myelitis the position of a late and
regressive stage. Erb admits that red softening, to which he also
assigns the position of a first stage, is very rarely seen, only
traumatic and rapidly fatal cases of central myelitis offering
opportunities of examining it. None of the {814} various forms of
exudation claimed to occur at this period under the names of vitreous,
colloid, or hyaline deposit have been confirmed in any recently
well-studied case.[88] The great mass of authorities, however, still
agree in regarding the minute changes of the initial stage of myelitis
to correspond to those of ordinary inflammation. The vessels are
described as injected, the adventitial spaces as crowded with the
formed elements of the blood, and the vascular walls and the neuroglia
infiltrated with granule-cells and fatty granular matter. By some,
inflammatory changes of the neuroglia are described, but I am unable
to find a single case in which these were determined in early fatal
cases. As far as our observation goes, the hypertrophy of the
neuroglia is a later occurrence.
[Footnote 87: _A Treatise on Diseases of the Nervous System_, 1882,
vol. ii. p. 280. The author states no authority, nor does he advance
his own observations in support of this statement.]
[Footnote 88: Baumgarten's case of hyaline exudation, _Archiv der
Heilkunde_, vol. xvii. 276, was an infectious myelitis and associated
with anthrax.]
As to the nervous elements themselves, they are always found affected.
The nerve-cells appear inflated, their processes fragile, sometimes
suddenly swollen in their course, at others very thin and brittle.
Multiplication of the nuclei of the large multipolar cells has been
described. It must be an unusual occurrence, as it has been confirmed
by but a few of the numerous observers who have examined into this
question. The protoplasm of the nervous elements loses its normal
striation and fine molecular granulation; it becomes either coarsely
granular or hyaline. The axis-cylinders, both in their intracinereal
and their intramyelinic course, show changes similar to those of the
cell-processes in the gray matter. Particularly frequent are swellings
in their course, the diameter of the cylinder being so much increased
as to almost equal that of the myelin tube. This increase in diameter
is regarded as an inflammatory swelling by some, as secondary to
disturbed nutrition by others; it precedes disintegration: the
substance becomes granular, fragile, and in the end dissolves. In the
mean time the myelin loses its continuity, irregular segments of it
fusing into round and oval masses.[89]
[Footnote 89: Many of the bodies represented as granule and colloidal
cells are in reality round spheres of myelin, whose resemblance to a
nucleated cell is sometimes heightened by their occasional inclusion
of a fragment of an axis-cylinder which has not yet lost its power of
imbibing carmine and other dyes. Where softening has proceeded
farthest, there the spherical and other forms of myelin are found
crowding the field, and mingled with them are blood-corpuscles,
fragments of blood-pigment, granular detritus, and bodies known as
fatty granular cells. A number of bodies of very different origin have
received this name, some of them, like the fragments of myelin alluded
to, not even meriting the name of cells. Others, however, are
veritable formed histological elements, either leucocytes or cellular
ingredients of the neuroglia, which, having fed on the products of
myelin disintegration, have become enlarged and coarsely granular. The
longer the duration of the process the more numerous are these bodies,
showing that they are not the coarse and essential factor of the
inflammation, but an accompaniment, subserving some conservative
process, inasmuch as they either remove effete material or contribute
to the permanent organization of the cicatricial or atrophic tissue.]
The period now reached by the morbid process may be regarded as a sort
of interregnum. The necrotic tissues have not yet disappeared on the
one hand, the products of inflammation have not yet organized
themselves on the other. It is in this period that the ganglionic
elements are described as undergoing certain changes in outline and in
appearance. Above all, one change has interested observers, which,
consisting in the development of what appear to be spherical vacuoles
in the interior of the cell, is termed vacuolization. I can compare it
to nothing so nearly as to {815} the appearance which is produced by
the formation of gas-bubbles in a putrefying albumen or other
semifluid substance.
This vacuolization of ganglion-cells is now regarded as a cadaveric
change. It is not agreed, as yet, whether its occurrence in myelitis
is so frequent as to suggest its ante-mortem occurrence as a veritable
feature of the disease. I have been struck by this change in the
neighborhood of wounds artificially produced in dogs, even in the
fresh specimen. It must be remembered, however, that under these
circumstances, the nutrition of the cell being destroyed and exposure
to the macerating effect of the cerebro-spinal and pathologically
exuded fluids occurring, a cadaveric change may take place intra
vitam.
The influence of phosphorus and alkaloid as well as metallic poisons
on the cord has been experimentally studied by a number of observers.
Unfortunately, Popow, Tschisch, and Danillo—who described as
characteristic a resulting change in the staining reaction of the
cells, the development of vacuoli in them, and an atrophy of their
processes—had not made a sufficient number of examinations of normal
cords under like methods of preparation to recognize which of these
deviations is without the physiological confines. Kreyssig[90]
demonstrated the existence of all these conditions in the cords of
perfectly healthy animals preserved in chromic acid;[91] and Schultze
confirms him, and expresses a surprise, which must be shared by all
reflecting investigators, that poisons of so widely different a
character should have an identical effect on the cord-substance, as is
claimed by the writers named.
[Footnote 90: _Virchow's Archiv_, cii.]
[Footnote 91: He attributes the remarkable difference in staining of
nerve-cells of the same ganglionic group and in the same section to
the sudden transferral of the hardened specimens to strong alcohol,
which seems to be the custom in some German laboratories. He claims
that uniformity in staining is effected if the specimen be transferred
from the chromic preparation to weak alcohol, then to stronger, and
thus by gradual increase of the strength to strong spirit. Possibly,
instead of approximating the real structural indications by this
method, Kreyssig may obliterate them. In specimens which alcohol is
not permitted to touch before staining is completed, very deeply and
very lightly stained cells will be found almost side by side. The
shorter the hardening process, the more perfect the staining method,
the more likely are these differences to be found. It is reasonable to
assume that the difference in dye-absorbing power indicates slight
differences in the cell-protoplasm, marking the nutritive state of the
latter and occurring within physiological limits.]
If life be prolonged and the conservative processes assert themselves,
the disintegrated material disappears, and as the white color of the
greater area of the cord was due to the myelin, and the latter has now
become destroyed within the diseased area, the latter presents a
grayish color. This phase is often termed gray softening. The
consistency is, however, much firmer than in the previous stage.
Trabeculæ of connective tissue form, enclosing in their meshes a large
number of neuroglia-nuclei and sometimes spaces filled with fluid.
According as condensation and retraction or rarefication preponderate
the process will terminate either in the formation of a sclerotic
focus or of a cyst. Occasionally an irregular spongy tissue containing
several small cysts results.