Sir B. Brodie, who has given the clearest as well as the most succinct description of caries of the spine we have met with, considers that its pathological history may be arranged under three heads.
1. " It has its origin in that peculiar sof tened and otherwise altered condition of the bodies of the vertebrw, which seems to be connected with what is called a scrofulous state of constitution. In these cases ulceration may begin on any part of the surface, or even in the centre of the bone, but in general the first effects of it are perceptible where the interver tebral cartilage is connected with it and in the intervertebral cartilage itself."* As this is an instance of scrofulous caries, such as has been already noticed, it should perhaps have come more legitimately under consideration in that part of our article. We prefer, however, to take a distinct and sepamte view of caries of the spine, because the locality invests the disease with some peculiarities. For instance, this scrofulous caries is almost invariably attended by abscess, and we find. these collections to be much larger in quantity of contents, and, if possible, more sluggish in approach to the surface than when situated elsewhere. Their existence, therefore, may not only not be suspected, but the symptoms occa sioned by them during life may be attributed to a totally different cause. They are least frequently met with in the neck, but when so situated it is easy to conceive how they may occasion dysphagia or difficult respiration. We have seen a case where such an abscess occasioned symptoms resembling those of com pression of the brain, and we have the notes of one in which death was produced in a very sudden and unexpected manner, the matter having burst into the sheath of the spinal marrow. They may also occur in connexion with disease of the dorsal vertebrw, and within the chest give rise to symptoms resembling the different forms of deranged respiration—tho racic aneurism—and, under peculiar circum stances, even of empyema. Such difficulties are now not so likely to occur, as we have • auscultation to assist the diagnosis ; but we recollect to have seen more than one case treated as a pulmonary affection, the real nature of which was caries of the dorsal vertebrez, complicated with abscess pressing forward within the posterior mediastinum. Abscess in the loins connected with diseased vertebree is too familiar an occurrence to require any lengthened details.
As far as our own observation can guide us, we believe the appearance of abscess as an accompaniment of spinal disease to be almost always a fatal symptom ; and when, in the course of a wasting and protracted discharge, spiculee of carious bone, or •portions of a sub stance resembling ivory or enamel are seen to come away, the aspect of the case is still farther formidable—very few, if any, ever recover under such circumstances.
2. " In other cases the vertebr2e retain their natural texture and hardness, and the first indication of the disease is ulceration of one or more of the intervertebral cartilages, and of the surfaces of bone with which they are con nected." " There is still another order of cases, but these are of more rare occurrenee, in which the bodies of the vertebrze are affected with chronic inflammation, of which ulceration of the intervertebral cartilages is the consequence." We shall now proceed to detail the results of our own observations, in order to see how far they coincide with those of the learned and accurate surgeon already quoted.
In two instances we have, in the dissecting room, seen the intervertebral substance eroded at the anterior edge, the bodies of the adjacent bones remaining unaltered in shape or consis tence, and to every appearance in a perfectly healthy condition. These were, at the time, regarded as specimens of the very earliest and incipient stage of the disease, and although no clue could be obtained as to the history of the cases, it is worthy of remark that not a trace of scrofulous disease could be discovered in any other parts of the bodies.
In general, however, it is otherwise. The body of the bone seems to be seized with scrofulous inflainmation, and the peculiar ef fects of this morbid action are produced within it. It becomes softer in consistence, in conse quence of the absorption of its osseous parti cles, and a deposition of the cheesy lymph in its stead. At this time, although so soft as to admit of being cut with a knife, the bone ap pears unaltered as to size or shape, but its absorbents begin to act upon the ligaments and intervertebral cartilages, and hence is it that the separation and ulceration of these are amongst the earliest appearances. In many instances the connexion between the cartilage and bone is so much impaired, that if we wanted to separate them with a knife, the former would come off in one entire flake. The edges then begin to be eroded and ulcerated, as if gnawed by a mouse ; and at this period also the ligaments are often found thickened and softened, and matted up together into a confused and indistinct mass. The body of the bone then becomes carious, and the ulce ration commences at the anterior part of it : very rarely is the posterior layer of firm bone, that forms the front of the canal for the spinal marrow, affected; and never does the caries spread to the processes. Up to this period it may be, and often is, a specimen of purely dry caries, being unattended by the formation of a single drop of purulent matter.