CHAPTER XII.

THE ARACHNOID AND PIA MATER OF THE SPINAL CORD.

ALTHOUGH the anatomical connection between these membranes is somewhat different from that obtaining between the cerebral meninges, it does not appear that their relation in disease differs materially from what we have found to prevail in that locality; we shall, therefore, consider them together.

The absence of valves in the spinal veins, and their peculiar distribution, cause the circulation of the spinal cord to be very sluggish, and, therefore, prone to congestion and stagnation; to this, Ollivier attributes the great number of dilatations which we find in the different points of its extent, in individuals advanced in years. He adds, that he has generally remarked that the quantity of serum in the vertebral canal was so much the greater, according as there was a greater congestion in the veins of the spine, and of the membranous coverings of the cord; thus, the slowness and difficulty of the course of the venous blood may be here the causes of a dropsy, which is independent of inflammation of the spinal membranes. These effusions of serum will, according to the exciting causes, be of a chronic or acute character; in infancy, irritation frequently gives rise to a more rapid accumulation of fluid, while in old age a slow effusion is frequently met with, which Rokitansky attributes, in part, at least, to a secondary congestion, arising from atrophy of the medulla and the roots of the nerves. The fluid exhaled under such circumstances will follow the law of gravitation, and accumulate at the lower end of the spinal cord, and thus assist in exciting and perpetuating paraplegic symptoms of which we may be unable to detect a sufficiently satisfactory reason after death. The occurrence of sanguineous apoplexy of the meninges, in any form, is very rarely met with; Dr. Abercrombie gives a single instance, which occurred under his own observation, in a child, aged seven, in whom, after an illness of three days, death ensued after violent convulsions. A long and very firm coagulum of blood was found, external to the cord, extending the whole length of the cervical portion. An interesting case of hemorrhage under the pia mater, but external to the cord, is also quoted, from Dr. Stroud's notes, by Dr. Bright (p. 340). Numerous instances of spinal apoplexy occurring in children are given by Dr. Mauthner, but as no post-mortem appearances are recorded, the inferences are solely derived from the symptoms, which do not enable us to state positively the exact nature of the effusion. We possess more satisfactory and copious evidence regarding the inflammatory affections of the spinal meninges, and it appears that it is a

very frequent cause of death in new-born infants; thus, Billard found, that in thirty cases of convulsions, there was meningitis of the cord in twenty, only six of which presented inflammation of the cerebral meninges. It is much less frequent in the adult, and is here almost invariably associated with, or consequent upon, cerebral inflammation. As a result of an acute inflammation of the membranes, we find lymph, or pus exuded, to a greater or less extent. Either may invest the entire surface of the cord, or it may be limited, as in a case that fell under our own observation, in a child of four years of age, to a space of an inch and a half in length. But we must be careful in at once concluding that we have to deal with a case of spinal meningitis, because we find the theca vertebralis lined with pus, for it may find its way from without into the cavity; thus, in a case of psoas abscess, given by Dr. Bright, the sudden supervention of fatal symptoms was manifestly due to this cause; a probe could be easily passed from the intervertebral foramina into the adjoining abscess. In the chronic form of spinal meningitis, the traces of the disease consist in greater or less opacity and thickening of the arachnoid, which frequently is found closely adherent to the spinal cord, and corrugated.

3

The symptoms of spinal arachnitis are met in trismus neonatorum, in the shape of congestion of the spinal arachnoid, with an effusion of blood or serum into its cavity; and Dr West' also states that, in the three cases which he examined, he found effusion of fluid or coagulated blood in the cellular tissues surrounding the theca of the cord. This is not necessarily at variance with the statements of Dr Schöller and Dr. Colles, who attribute trismus to inflammation of the umbilical arteries, as this may, and is, found to coexist with the former. Symptoms of inflammation of the spinal membranes have also been met with in tetanus; but in by far the greater number of cases examined after death, no uniform or adequate cause, to which the symptoms were referable, could be discovered. The importance of the predisposing causes is, probably, as great in tetanus as it is shown to be in trismus; atmospheric states have a manifest influence in this respect, and an irritation set up in any part of the body, and propagated to the nervous centres, under such circumstances, induces the disease. The same absence of uniform pathological data exists in another disease, which we cannot but refer to the nervous centres, hydrophobia; congestion of the cerebro-spinal membranes and nerve-matter, and some occasional effusion, is all that is generally met with in the shape of post-mortem effects; we need not add that these appearances cannot be considered as characteristic of the disease in question. Mr. Youatt, whose extensive experience of hydrophobia in the brute creation, justifies our referring to him as an authority, states that the appearance of inflammation of rabies is of a peculiar character in the stomach, but that no conclusion can be drawn from the state of other organs. In discussing the changes occurring in the spinal cord itself, we shall have occasion once more to recur to the subject of tetanus.

The Diseases of Infancy and Childhood, p. 125.

2 Neue Zeitschrift für Geburtskunde von Busch, D'Outrepont und Ritgen, vol. v. p. 477. 3 Dublin Hospital Reports, p. 285.

In cases of long standing paralysis and paraplegia, we find evidence of chronic meningitis of the cord in the corrugation, opacity, and close adhesions of the membranes to one another, and to the cord. A good illustration of this is afforded by a case given in Dr. Bright's Reports (page 380); here, the dura mater of the cord was unusually firm and thick, and, as far as the middle of the back, closely adherent to the pia mater, from which, in most parts, it could not be detached without lacerating the cord. On attentive examination, it was found that the apparent thickening of the dura mater depended chiefly on a layer of membrane, of almost cartilaginous thickness, beneath it; and was, probably, rather the diseased arachnoid, or an adventitious deposit, than the dura mater itself. These appearances may be associated with further lesion of the cord, or with adventitious growths of the vertebral column or arachnoid. The only growths of this kind that are of frequent occurrence, are formations of bone on the visceral side of the latter membrane. In this respect, we perceive a characteristic distinction between the head and the spinal column; for while, in the former, ossific deposits are common in the dura mater, and are scarcely ever met with in the other membranes, in the spinal column they are found to prevail in the arachnoid, and not to affect the dura mater. A remarkable instance is recorded by Herbert Mayo, in his Outlines of Human Pathology, of osseous concretions surrounding the posterior roots of the nerves, and proceeding to the lower extremity. This, undoubtedly, belonged to the class of pathological products under consideration; and the case has a special interest, from its bearing upon an important law of nervous conduction. The pains suffered by the patient were so limited to the lower extremity, and were so excruciating, that the surgeon performed amputation of the limb, though with what results need scarcely be stated.

Cartilage also forms, though less frequently, on the arachnoid. A good instance is recorded in the Reports of the Pathological Society of London, by Dr. Quain,' who describes the lamina as composed of a transparent matrix, in which were deposited small cells, containing nucleoli, and numerous small amorphous granules.

It does not appear that there is a liability on the part of the spinal pia mater to tubercular deposit, as we find to prevail in the cerebrum. Rokitansky remarks on the subject, that he has never had occasion to suspect the exudation formed on the pia mater to be of a tuberculous. nature, and that this observation accords with the fact that spontaneous spinal meningitis so commonly coexists with that form of cerebral meningitis which produces similar exudations. An acute tuberculosis, he adds, he has never observed in it.

Reports, &c. 1849, p. 25.

CHAPTER XIII.

THE SPINAL CORD.

THE forms of disease and their effects, which present themselves in the spinal cord, closely resemble those we meet with in the brain. The spinal cord does not appear to be so often attacked as the encephalon, and as we have already pointed out, it is the part which is generally left unexamined, unless attention is forcibly directed to it by the previous symptoms of the patient; for both reasons the records of its pathological states are much more scanty than those regarding the brain, and future inquirers have yet a large field to explore. The evanescent character of congestion rarely allows of its being demonstrated after death; though it is impossible to believe that there should not be accumulation of blood in the cord, in those instances in which

Fig. 129.

the symptoms demonstrate intense irritation of the part, as in tetanus; a case of hydrophobia is recorded by Dr. Bright, in which a blush of redness was perceived in the cineritious part of the spinal cord opposite the second and third cervical vertebræ. An anæmic condition of the cord is as difficult to demonstrate at its converse, though here too the practitioner will not fail to suggest instances in which its existence may be fairly assumed during life. Both states manifest themselves in the secondary effects of hypertrophy and atrophy. These may be general or local; the former affection belonging chiefly to early life, and the latter, like the corresponding condition in the brain, to old age. Atrophy of the spinal cord is one of the pawith angular curvature of thological conditions met with in the disease known as tabes dorsalis; in this case it is more of a local character, involving only the lumbar segment of the cord and the nerves passing off from that part. The separate divisions of the cauda equina are often found entirely deprived of their medulla, and nothing but the neurilemma may remain. A local atrophy, as the effect of the compression exerted by morbid growths or displacement of the vertebra is frequently met with, and in these cases it is of peculiar physiological interest to observe the limitation of the symptoms of nervous affection according to the extent to which the pathological condition involves the

Part of a spinal cord from a case of paraplegia,

the spine, in a lad aged eighteen. Opposite the contracted part of the cord, a short process of bone projected from the angle of the curvature into the spinal canal.- From St. Bartholomew's Museum, Series vii. No. 7.

medulla. Numerous instances are recorded by writers on the subject; among whom we would particularly refer to Ollivier, Longet, and Romberg. Both in atrophy and hypertrophy of the spinal cord, the tissue is commonly indurated and firmer than in the normal state.

Cases of the termination of myelitis, or inflammation of the cord, in the first stage, like those of encephalitis, are scarcely ever met with; it becomes the question whether, owing to the peculiarity of the nervous structures, the first onset of inflammatory action is not at once accompanied by those changes, which in other tissues are looked upon as the secondary products of inflammation. An essential difference appears to prevail between the brain and spinal cord with regard to one of the results of congestion, hemorrhagic effusion. The frequent occurrence of apoplexy of the encephalon is familiar to all; its idiopathic occurrence in the spinal cord is extremely rare, and when brought on by external lesion, such as fracture of the vertebræ, or penetrating wounds, it is commonly associated with hemorrhage on the surface. The cases collected by Dr. Abercrombie all appear to be instances of effusion between the meninges and the cord itself. The rarity of the occurrence may justify our extracting the following observation from the Report of the Pathological Society for 1849, p. 28:

"A gentleman, aged 44, who, with the exception of occasional attacks of gout, had previously enjoyed good health, was suddenly seized one evening with violent spasm in the stomach, and found that he had lost all sensation and power of motion in the lower half of the body. Mr. Curling found him an hour later with complete paraplegia below the third ribs, and strong priapism; no excito-motory movements were producible, and the mind was perfectly clear. The priapism subsided in about twenty-four hours; there was no extension of paralysis, except a feeling of numbness of the hands, and at last imperfect power of using them. During the first eighteen hours after the attack, scarcely any urine was secreted, and it subsequently became scanty in amount. The patient died four days after the seizure. The spine was examined seventeen hours after death. The muscles of the back were much loaded with blood-no fluid escaped on opening the theca vertebralis, the head being in a depending position. The vessels on the surface of the cord were a good deal congested. An incision was made above the front of the medulla, commencing at the part corresponding to the third cervical vertebræ, and terminating at the last dorsal; two small clots of blood, amounting together to about a drachm, were found in the interior of the medulla, occupying about an inch and a half in extent, and situated between the origins of the second and third pairs of dorsal nerves. The substance of the cord around the clots was somewhat soft; the medulla was more or less infiltrated and stained with blood from the site of the clots upwards as high as the third cervical vertebræ, and downwards as low as the last dorsal."

No microscopic examination of the parts appears to have been made; future observation must determine whether atheromatous, or other degeneration of the arteries, or previous derangement in the nutrition of the adjoining tissues, is the causa proxima of spinal, as it so frequently is of cerebral hemorrhage. The above case does not tally with the statement