Chapter LIX: Part 59

The glandulæ concatenatæ of the neck are apt to be enlarged from the chronic engorgement. Watson mentions a case in which this added so much to the volume of the neck as to give a superficial resemblance to goitre.

Occlusion of the inferior vena cava produces, if life is continued, an immense dilatation of the veins of the abdomen and of the thighs. By compressing the abdominal veins it can be seen that the blood-current is reversed, flowing upward through vessels anastomosing with the intercostal and internal mammary veins. Internally, the circulation is carried on chiefly by the azygos, which may become as large as the normal cava.

{852} There is usually, but not always,[16] an extreme degree of ascites, together with anasarca of the lower half of the body. After a time, however, as the tributary circulation becomes established, the effusion will be reabsorbed.

[Footnote 16: _Le Progrès Médical_, May 26, 1877; _Med. Record_, July 28, 1877.]

If the obstruction involves the portal vein, the ascites will be still more marked. In this case there is also enlargement of the spleen. When the cava is occluded above the point at which it receives the renal veins, congestion of the kidneys results, which in time produces interstitial change. Yet even here the establishment of the collateral circulation may be sufficiently prompt to avert the danger.

Anomalies of the cava are occasionally observed. Osler has reported a case in which the inferior cava was represented only by a fibrous cord. The condition was probably congenital.[17] Greenfield mentions a case in which the descending cava was absent, both brachio-cephalic trunks passing into the heart by the coronary sinus.[18]

[Footnote 17: _Journal of Anatomy and Physiology_, April, 1879.]

[Footnote 18: _Med. Times and Gazette_, April 22, 1876.]

If the cause of the occlusion of either cava be not such as of itself to destroy life, the patient may get on with some degree of comfort for many years. The establishment of the collateral circulation sometimes keeps pace with the increasing obstruction, so that little or no ascites or oedema occurs.[19]

[Footnote 19: Turpin, "Obliteration Inf. Vena Cava," _N. O. Med. and Surg. Journal_, 1881, p. 575.]

The TREATMENT of obstruction of either of the venæ cavæ can, as a rule, be only palliative. In the great majority of cases the cause is entirely beyond our reach. All violent muscular exertion, making an excessive demand upon the circulation, should be avoided. While the blood should not be impoverished, as that would favor dropsical effusions, the patient, on the other hand, should not be allowed to become plethoric through the influence of his enforced sedentary habits. The diet should therefore be light and digestible, and over-feeding should be carefully avoided. The occasional use of saline purgatives may be required. Dropsical accumulations may call for the administration of diuretics or drastic cathartics, and perhaps for tapping.

Occlusion of the vena portæ, by obstructing the return of the blood from the intestines, gives rise to rapid and abundant effusion into the abdominal cavity. As the gastric vein cannot empty itself, there is congestion of the stomach, often ending in hemorrhage, the blood being both vomited and passed by stool. The spleen also is enlarged by passive engorgement, its vein depending upon the portal for an outlet. This assemblage of symptoms renders the diagnosis almost positive.[20] There is no enlargement of the liver unless the hepatic vein is also involved.

[Footnote 20: An interesting case is reported by A. A. Smith in the _N.Y. Med. Journal_, January, 1880.]

Paget maintains that the occlusion of the principal vein of a limb may result in an increased growth of some of the tissues, especially of the muscles.

Degenerations.

Fatty degeneration is rarely observed in the veins, but it occasionally occurs in those which have long been subjected to excessive strain, which by compressing the nutrient vessels affects the nutrition of the walls.

Calcification is less rare. It results in the formation of plates or rings which closely resemble bone in their structure. Such plates may not unfrequently be felt in old superficial varicose veins. Sometimes these formations project as spines into the lumen of the vessel, and, coagula forming about them, a thrombus is the result.[21]

[Footnote 21: See preceding reference.]

{853} Cancer of the veins is rare as a primary affection, but it is not uncommon when the vessel traverses a cancerous mass. The morbid process readily penetrates the thin wall of the vessel, and cancerous nodules form on the inside and become the starting-point of thrombi which are soon permeated and supplanted by the heterologous growth. This is sometimes moulded to the shape of the vein, and fills it for some distance in the form of a cylindrical plug. Fragments may be swept away in the blood-current and give rise to secondary cancer at the point of arrest in the liver or lungs. Virchow has described a case of primary sarcoma of the inferior cava.

The existence of syphilitic lesions in the veins has not been satisfactorily demonstrated. It is positively denied by some authorities, while certain appearances found in the veins, especially of new-born children, are attributed by other writers to syphilitic inheritance.

Phlebolithes.

Vein-stones are roundish, oval, or cylindrical bodies found in the veins or in pouches connected with the veins, or sometimes in the connective tissue adjacent to a vein. Their size varies from that of a hempseed to that of a nutmeg. Externally they are white, but when divided they are found of a yellowish color at the centre. There is generally a central cavity, around which are disposed concentric laminæ such as are observed in vesical calculi. Chemically, these bodies are composed of an animal substance in which are deposited phosphate and carbonate of lime, and sometimes magnesia. The inner part is hard and brittle, the outer softer and more earthy.

Usually, phlebolithes are found loose in the vein, but if large they may be firmly impacted in the vessel, causing complete obstruction. Sometimes the outer portion is of a gelatinous texture, from which a delicate mesh extends to the wall of the vein and becomes incorporated with it.

Frequently these concretions occupy sacs or diverticula connected with the vein. Occasionally these sacs become detached from the vessel and are absorbed and removed, and the stone, then entirely outside of the vein, becomes enveloped in a fibrous cyst formed from the surrounding connective tissue.

Some doubt exists as to the manner in which these concretions are formed, but the probability is that a small clot first forms in the vessel, and that around this, as a nucleus, successive layers are deposited from the plasma of the blood. These layers then undergo chalky transformation by the deposit within them of salts of lime and magnesia. These formations seem to be conditioned by a slow current in a dilated vein. Hence they are most frequently found in the enlarged pelvic veins of old people, and especially about the neck of the bladder in those suffering from prostatic enlargement. They are also found in the varicose veins of the extremities.

Except in superficial situations they are usually not recognized during life. They seldom produce discomfort, and therefore rarely call for treatment. When accessible they may be excised if requisite, the vein being secured above and below if not already permanently occluded.[22]

[Footnote 22: Rokitansky, _Path. Anat._, Philadelphia, 1858.]

{854}

THE CAISSON DISEASE.[1]

BY ANDREW H. SMITH, M.D.

[Footnote 1: This article is mostly drawn from a report by the writer on _The Effects of High Atmospheric Pressure, including the Caisson Disease_, published in 1873 by the New York and Brooklyn Bridge Company.]

Persons exposed for a considerable time to a greatly increased atmospheric pressure are liable, after the pressure is removed, to certain morbid effects which comprise what is known as the caisson disease. It is observed principally in those employed in submarine operations by the aid of compressed air, and who labor for hours together in what is termed by engineers a caisson. The pressure varies with the depth at which the work is carried on, and reaches sometimes fifty or more pounds to the square inch. The disease rarely if ever occurs when the pressure is less than fifteen pounds, and its severity is, other things being equal, in direct ratio to the increase in the density of the atmosphere.

SYMPTOMS.--These are, in the order of their frequency, intense neuralgic pain in one or more of the extremities, and sometimes in the trunk; epigastric pain; nausea and vomiting; more or less complete paralysis, which may be local or general; headache; vertigo; and coma.

The pain, which is often very severe, is usually paroxysmal, exacerbations and remissions occurring at short intervals. It may come on suddenly in its full severity, or it may be slight at first and rapidly increase until it becomes absolutely intolerable, "as if the flesh were being torn from the bones." The pain begins most frequently in the knees, extending rapidly to the legs and thighs, but the upper extremities may be first attacked. Sometimes the most severe pain is felt in the spine, and especially in the lumbar region. There is usually some tenderness with the pain, and a stiffness of the muscles of the affected limbs.

Epigastric pain occurs in a considerable proportion of the cases. It is often very severe, and if not relieved by treatment is liable to be followed by nausea and vomiting. The vomiting is usually limited to the ejection of the contents of the stomach, but it may persist, sometimes even after the pain has ceased. Vomiting accompanied by giddiness may occur without epigastric pain, and is then probably of cerebral origin. Paralysis, to a greater or less degree, occurs with considerable frequency, the percentage of cases increasing in proportion to the pressure of the atmosphere to which the patients have been exposed and the duration of the exposure. It affects most frequently the lower half of the body, but it may include the trunk or one or both arms. In rare cases an arm alone is affected.

The paralysis is of sensation as well as motion. It comes on soon after the invasion of the pains, but affords no relief from them. Thus, while pinching or pricking occasions no pain, the part may still be the seat of exquisite suffering. Paralysis may, however, occur in cases in which the pain is very slight or entirely absent. The paralysis varies in degree from a transient {855} weakness of the limbs and slightly impaired sensation to complete loss of motion and sensation in the affected part. Even the minor degrees generally affect the bladder.

Symptoms of a transient character are often observed depending upon changes in the brain. They consist of headache, dizziness, double vision, incoherence of speech, and sometimes syncope. They usually pass off in a few hours. In fatal cases, however, coma is the usual forerunner of death.

The duration of the caisson disease is from three or four hours to six or eight days. When paralysis occurs it may continue for weeks, or it may pass off within twelve hours. The cases marked only by neuralgic pains do not generally last more than six to twelve hours, though some continue five or six days. Death occurs only in cases which are severe from the first and show symptoms of cerebral or spinal effusion.

MORBID ANATOMY.--The constant lesion in fatal cases of caisson disease is congestion of the brain or spinal cord. This congestion may be pretty evenly distributed or it may vary in intensity in different localities. This is especially true as regards the cord. It affects both the meninges and the substance of the brain or cord. In most cases there is more or less of serous effusion into the arachnoid. The tissues of the scalp and those surrounding the spinal column are sometimes engorged.

When sufficient time elapses before death the brain may be softened in spots. This is probably due to the occlusion of vessels by coagula formed during the primary congestion.

Congestions also occur in other localities, and especially in the solid abdominal viscera. The liver and spleen have been found engorged in nearly every case. Jaminet has found clots of blood in the kidneys.[2] The mucous membrane of the stomach, intestines, and bladder is often injected and marked with patches of ecchymosis. The lungs in cases of true caisson disease, though occasionally found in a state resembling red hepatization, seldom present any other change than simple hypostatic congestion.

[Footnote 2: _Physical Effects of Compressed Air_, p. 20.]

PATHOLOGY.--It is probable that the pathology of this disease is not entirely uniform in all cases. Doubtless the chief element in it is the congestions already described, and especially of the brain and spinal cord. The mechanism, therefore, of these congestions becomes a subject of paramount importance.

It was suggested by François[3] that the morbid phenomena might be due to the liberation in the vessels of air which had been absorbed by the blood while under pressure, but which was set free again when the pressure was removed. This theory has been reasserted by Paul Bert,[4] with this difference: that he claims that bubbles of nitrogen instead of air are the cause of the interruption of the circulation. These bubbles he has discovered after death in the vessels of the brain and cord. But he states that when the pressure does not exceed five atmospheres three minutes allowed for the restoration of the normal pressure will be found to prevent the formation of these globules of nitrogen. Now, we find the caisson disease occurring when the pressure does not exceed two atmospheres and when six to eight minutes are allowed for locking out.[5] It would seem that under these conditions the gas should escape through the lungs as rapidly as it is disengaged from the blood. Moreover, we find that the attack often comes on several minutes or even hours after leaving the caisson. During this time any free nitrogen in the blood should be constantly becoming less by diffusion through the {856} pulmonary membrane, and if enough were not present at first to cause obstruction, such an effect could scarcely take place at a later period.[6]

[Footnote 3: _Annales d'Hygien publique et de Méd. legale_, t. xiv., 1860.]

[Footnote 4: _Comptes Rendus_, August, 1872, and February and March, 1873.]

[Footnote 5: _I.e._ passing from the caisson into the open air through the lock, or antechamber, where the pressure is gradually reduced.]

[Footnote 6: In a private letter to the writer, T. Lauder Brunton suggests that a bubble of air might pass from a larger vessel, which it had only partially obstructed, into a smaller branch, which would be entirely occluded by it, or that additional nitrogen might be disengaged when the pressure was lessened by relaxation of vascular tension.]

It is also very difficult to reconcile with Bert's theory the fact of the comparative immunity from danger which results from repeated exposures to the effects of compressed air. If the action were that of purely physical causes, habit could make no difference. The obstruction of the vessels, as described by Bert, is a condition of which the system could never become tolerant by frequency of repetition.

In the writer's view, the explanation is to be found in the changed conditions of the circulation, which result first from the increased pressure upon the surface, and then from the sudden removal of the pressure. While the subject is in the caisson the blood is driven from the peripheral vessels toward the interior of the body, where the pressure is less than at the surface.[7] It is also forced from the more compressible tissues into the solid and resisting organs, such as the liver and kidneys; and lastly, it flows toward bony cavities, for the reason that their walls resist the effect of direct pressure, and equilibrium of pressure can be restored within them only by an afflux of blood. Thus the distribution of the blood is everywhere changed, and the size of the vessels is no longer determined by the muscular action of their walls, but by the amount of blood forced into them, the vital action which should regulate the circulation being entirely overpowered and set at naught by an overwhelming physical force operating from without. The vessels become merely passive tubes, distended in some places where they are protected from pressure, and compressed in others where the tissues about them are compressible. By this transfer of blood from one part to another the equilibrium of pressure is restored and the circulation goes on, though without any regard to the physiological demands of the different organs. There is no stasis anywhere so long as pressure and counter-pressure are equal, thus allowing fair play for the action of the heart.

[Footnote 7: This is shown by the marked pallor of the skin and the shrunken and wrinkled appearance of the hands.]

If, now, the external pressure is suddenly removed, what will be the result? Vessels which have been compressed and almost emptied of blood will now offer new channels through which the blood can rush, and vessels overcrowded with blood, with their walls paralyzed by over-distension, will have the current within them slowed almost or quite to the point of stopping. The vessels of the brain and spinal cord, being within bony walls, where the direct pressure of the condensed air could not affect them, will be found the most distended and the most helpless to relieve themselves. They will get little aid from the vis a tergo of the circulation, for the blood will find easier courses by other ways, vascular tension being almost nil and the vaso-motor system out of use.

The longer the sojourn in the caisson has been, the more entirely passive the vessels will have become, and the longer will be the time they will require to resume their normal condition. At some points the circulation will be greatly slowed or entirely interrupted, and nerve-elements lying beyond and deprived of their blood-supply will express their want by pain or paralysis. Areas of stasis once formed will be likely to extend, and may thus affect nerve-elements which at first escaped. This would explain those cases in which the attack is deferred until some time after leaving the caisson.

It is readily conceivable that in persons beginning work when the pressure is slight and continuing day by day, as the pressure slowly increases the {857} vessels should acquire the power of adaptation to the variations in the amount of their contents, since this is only an extension of the physiological principle which we see exemplified in all organs having an intermittent function.

The influence of the trophic system of nerves also, as the connecting link between central nerve-lesions and peripheral vascular disturbances, must not be forgotten in this connection. Suspension of function in trophic cells, either in the cerebral cortex or in the anterior horns of the cord, could easily be brought about by the action of the mechanical causes already described, and would result in areas of vaso-motor paralysis and consequent congestion at the termination of the corresponding nerve-fibres. The proneness of the large joints, and especially the knees, to be attacked is suggestive, in view of the like circumstance in chronic degeneration of the cord.

CAUSES.--The one essential cause without which the disease can never be developed is transition to the normal atmospheric pressure after a prolonged sojourn in a highly-condensed atmosphere. Hence we have to consider two elements, pressure and time, the danger in these cases being as the degree of pressure to which the person has been exposed multiplied by the duration of the exposure.

But inasmuch as a prolonged sojourn in the caisson does not in every case produce the disease (many of the men employed escaping it entirely), it follows that there must be concurrent causes which determine its development.

The first of these is a special predisposition. This is occasionally strongly marked, some persons being affected by a short exposure to a low pressure from which there would generally be experienced no inconvenience whatever.

Perhaps the most frequent exciting cause of the caisson disease is too rapid locking out. Indeed, it is altogether probable that if sufficient time were allowed for passing through the lock the disease would never occur. But what is sufficient time for one is too short for another; and all that can be done is to fix upon a duration for the process which shall be proportioned to the pressure, and as great as is consistent with the circumstances, and then to see that the rule is rigidly observed. At least five minutes should always be allowed for each additional atmosphere of pressure.

Newness to the Work.--Unquestionably, the liability to the caisson disease is greatest in those exposed for the first time to the influence of the compressed air. New hands are very apt indeed to suffer more or less during the first week. Those least affected are such as begin work when the pressure is comparatively slight, and continue without intermission as the pressure increases. It seems that the system after a time becomes adapted to the changed conditions, and is protected in a measure from their effects. Nevertheless, some serious cases occur among old hands, especially when for any reason their stay in the caisson is prolonged beyond the usual time, thus showing that their immunity is merely relative. A sudden increase of pressure also, even though very slight, is certain to develop new cases, men thoroughly inured to the work often being affected under such circumstances.

Fulness of Habit.--During the progress of the work on the East River Bridge in 1872 the writer, who had medical charge of the men, observed that among those taken sick there was a very marked preponderance of men of heavy build and with a tendency to corpulency. Of 39 men of this build, only 3 escaped illness, while of 53 lank and spare men 25 escaped. Of the 39 stout men, 8 were more or less paralyzed; of the 53 slender men, only 2 were paralyzed. The deaths, 3 in number, were all of heavy men.

These figures show unmistakably that a tendency to fulness of habit renders work in a compressed atmosphere much more hazardous. Persons of this build have more fluids in the body, the distribution of which is changed by the pressure in the manner before stated, and it is therefore not surprising {858} that the effect upon them should be greater than upon lean and sinewy persons, whose bodies contain a minimum of fluid.

Severe Exertion immediately after Leaving the Caisson.--As at the moment of going out of the compressed air the system undergoes a violent reaction, it is manifestly unfitted to bear in addition a severe tax upon the muscular strength. Hence the ascent of a long flight of stairs immediately after leaving the air-lock is as wrong in theory as it has proved bad in practice. Triger, whose apparatus at Chalonnes was so arranged that the ascent of the ladder took place in the compressed air, the lock being placed at the top instead of the bottom of the shaft, found that the men ascended a distance of seventy feet without becoming in the least out of breath--making the ascent, in fact, more easily than if it had been in the open air.[8]

[Footnote 8: _Comptes Rendus_, t. xiii., 1841.]

The Abuse of Alcohol.--Several writers have remarked that habitual drinkers are more likely to be affected than those who used spirits moderately or not at all. It is stated by the director of the work at Douchy[9] that the attacks from which the men suffered were "almost always coincident with some excess committed in the interval of the shifts." It is easy to perceive that, as the disease is characterized by cerebral congestion, the abuse of alcohol, which has a tendency to produce the same result, would act as a predisposing cause.

[Footnote 9: _Annales d'Hyg. pub. et de Méd. legale_, 1854.]

Entering the Caisson Fasting.--Jaminet insists very strongly upon the influence of this cause, and cites instances to prove his position. Several cases corroborative of his views occurred under the observation of the writer. One of the rules for the men working in the New York caisson prohibited entering the compressed air without having taken food, and in addition to this each new hand was especially cautioned as to the danger of disregarding this precaution, and the foremen were directed to use every effort to secure its observance. Yet, notwithstanding all this, a number of very severe attacks were found to be coincident with, if not dependent upon, violations of this rule. In these cases epigastric pain and retching were prominent symptoms.

TREATMENT.--The treatment of this disease will depend upon the severity of the case and the presence or absence of gastric symptoms or of paralysis. If we have to deal with the neuralgic pains only, the chief reliance must be upon anodynes administered with a liberal hand. Fortunately, the pain, though very severe while it lasts, is in most cases of short duration, the attack passing off usually in a few hours. It is therefore quite practicable to keep the patient under the influence of morphine during the whole time, and thus enable him to escape entirely all extreme suffering. But large doses will be required, the intense pain inducing a remarkable tolerance of the drug. Half a grain may be given at the outset, and a quarter of a grain every half hour afterward until relief is obtained. When employed hypodermically somewhat smaller doses may be used.

In some instances the very best results are obtained from hypodermic injections of atropine at the seat of pain, but in other cases they fail to procure relief, and, upon the whole, atropine is inferior to morphine.

Jaminet, regarding the affection as wholly the result of exhaustion, relies entirely upon stimulants and concentrated nourishment, ignoring the aid of anodynes altogether. It is difficult to see the reason for this, even admitting to the fullest extent his theory of the disease, for nothing can be more exhausting than the intolerable pain which characterizes this affection, and nothing could act more promptly as a restorative than an efficient anodyne.

Starting from the theory already given as to the mode in which the disease is produced, the writer was led to the idea that benefit would be derived from {859} the use of an agent that would induce contraction of the capillaries, and thus correct the want of tone which was considered to lie at the foundation of the difficulty. For this purpose ergot was employed, with the belief that it would be useful, first, by contracting the vessels of the brain and spinal cord and relieving their congested state; and, secondly, by restoring tone to the superficial vessels, and thus imparting vigor to the circulation.

An extended trial warrants him in saying that the results justified the theory. In his hands, though not always successful, ergot was certainly very useful in a considerable number of cases. He has seen very severe pain completely relieved within half an hour after the administration of a drachm of the fluid extract. In other instances unsteadiness of the limbs, which seemed about to usher in paralysis, yielded promptly to one or two doses. A teaspoonful of the fluid extract may be given, and the dose repeated in half or three-quarters of an hour, unless the pain is relieved.

Frictions, with or without stimulating liniments, are very generally resorted to, and seem sometimes to give momentary relief, but it appears to be rather by occupying the attention of the patient than by any action occasioned in the part. In some instances, when the pain is confined to a particular locality, having the part immersed in hot water will afford temporary relief. But the use of the general hot bath is not advised, as it is unsafe to increase the already existing relaxation of the vessels. In several of Jaminet's cases paralysis came on while in the hot bath. In two of the writer's cases cold was applied to the spine, with apparent benefit in each.

Epigastric pain is almost always relieved at once by the use of an alcoholic stimulant with ginger, as employed by Jaminet.

Vomiting is best treated with sinapisms to the epigastrium and swallowing small bits of ice.

When paralysis occurs it is to be treated on general principles. Cups or leeches, with douches and frictions to the spine, may be useful; and, if the case be protracted, the use of strychnine may be called for. Electricity may be of service in preserving the nutrition of the muscles. The bladder will almost certainly be involved, requiring the constant use of the catheter.

The cerebral symptoms which occasionally occur are, with the exception of coma, so transient in their nature as to call for no special treatment. Coma, when it takes place, is to be managed according to the circumstances of the case, as when proceeding from other causes. If accompanied by a full, strong pulse, venesection may be expedient.

There remains to be considered a plan of treatment originally suggested by Pol, and carried out to some extent by Foley--viz. returning the patient at once into the compressed air. Foley says, as the result of his experience, "A true specific is returning to the caisson, through which means all such accidents (pains, vertigo, etc.) speedily disappear. It is to be resorted to unhesitatingly in all threatening cases, and the pressure should be admitted rapidly." But the means of access to the caisson are usually such that it would be difficult to remove a patient into it, even if he could be comfortably cared for while there or if his presence would not interfere with the work. It would therefore be desirable to have facilities for employing compressed air at some point above ground which would be easily accessible.

Of course the secondary effects which arise in protracted cases would not be capable of direct relief by simply reproducing the physical conditions existing in the caisson. The most that might be hoped for in such cases would be that the pressure might result in giving a new impulse to the circulation in the congested part, and thus favor resolution.

Reasoning from his view of the pathology of the disease, Bert has proposed the inhalation of oxygen in order to displace the free nitrogen from the blood by diffusion. Experiments upon animals demonstrated that the sounds {860} produced in the heart by the presence of free nitrogen speedily disappeared when the animal was made to inhale oxygen, the nitrogen diffusing into this gas much more readily than into common air. But, though immediate death was averted by this expedient, paralysis nevertheless occurred, and the post-mortem examination showed the presence of bubbles of nitrogen in the vessels of the cord.

{861}

DISEASES OF THE MEDIASTINUM.

BY EDWARD T. BRUEN, M.D.

Inflammation of the Mediastinum.

SYNONYMS.--Mediastinitis. _Fr._ Médiastinite; _Ger._ Mediastinitis.

Lesions caused by inflammatory processes in the mediastinum may, theoretically, occur in the duplicatures of the pleura, separating the pleural from the mediastinal cavity. This condition may terminate in resolution or in effusion of plastic lymph, as in a case reported by Wildemann, in which the anterior mediastinum was filled with layers of solid exudation, the pericardium inflamed, and its cavity distended by six ounces of pus. The effusion appeared to have been occasioned by long-continued pressure on the sternal region. The process is practically unrecognizable during life, or at least possesses no described clinical features.

Abscess of the Mediastinal Space.

Galen has alluded to trephining of the sternum for caries or necrosis inducing the formation of pus; and Petit[1] has furnished many instances of mediastinal abscess from the warfare of preceding centuries.

[Footnote 1: _Traité des Maladies chirurgicales_, tome i. p. 143.]

ETIOLOGY.--I. Predisposing Influences.--Mediastinal abscess is very rare, at least of such dimensions as to simulate tumor. The condition is sometimes idiopathic, possibly due to sudden exposure to cold,[2] or is associated with the rheumatic diathesis, but in these cases some forgotten injury may have been received.

[Footnote 2: Gunther, _Oesterreich Zeitschrift f. Prak. Heilk._, 1859; Gross, _System Surgery_.]

Symptomatic or secondary purulent collections may occur in connection with operations upon the neck, as tracheotomy, also from softening gummata or glanders, or they may be due to a constitutional cause, the so-called metastatic inflammation of the mediastinal connective tissue in the course of pyæmia.

Scrofulous suppuration of the lymphatic glands may result in secondary abscess.[3]

[Footnote 3: Bristowe, _Path. Soc. Trans._, London, vol. ix. p. 46.]

II. Exciting Causes.--The mediastinum has been penetrated by balls and sabres, and in one case the shaft of a carriage passed through the anterior space, yet without damage to the contained viscera. Gunshot fracture of the sternum, recorded in the history of the Civil War in America, seems to have been very rarely followed by suppuration, even though the tissues have been exposed to such a degree as to render the arch of the aorta distinctly visible.

The anterior mediastinum may be threatened with inflammation, which may sometimes terminate in abscess, as in cases of caries, necrosis, or fracture of the sternum.

{862} Warner[4] reports a case in a boy aged thirteen in which two weeks after fracture of the sternal bone a separation of the edges of the fracture was observed, the interval being occupied by a tumor of considerable size, which contracted and dilated with as much regularity as the heart. It receded on palpation, and on removal of the pressure the tumor immediately resumed its former size. It subsequently ruptured, discharged the contents of an abscess, and the patient recovered.

[Footnote 4: _Amer. Journ. Med. Sci._, Apr., 1873.]

Goodhart[5] records a case of acute mediastinal abscess resulting apparently from injury produced by the sticking of a piece of meat in the oesophagus. A case illustrating the possibilities of direct injury to this region by a blow or fall has been recorded by Bennett. In a middle-aged lady, previously in good health, an abscess slowly formed and presented a prominence over the upper part of the sternum. Two months before the lady had fallen in going up stairs, and struck the sternum against the stone edge of the stairs. These examples have been selected because they seem to cover the possibilities of directly determining causes.

[Footnote 5: _Path. Trans._, London, vol. xxvii.]

SYMPTOMS.--There are three separate groupings under which the symptoms may be classified: _(a)_ The latent symptoms, which include chiefly manifestations of intra-thoracic irritation or pressure; _(b)_ the fulminating phenomena; _(c)_ the physical signs.

As a rule, mediastinal abscess is accompanied from first to last by deep-seated and gradually increasing pain and tenderness on pressure over the sternum; but it may be a sense of constriction and oppression with boring or throbbing sensations. Sometimes there is merely a sense of uneasiness about the chest, with pains of a rheumatic or neuralgic character in the shoulders or neck, brought about by irritation of the intercostal and humeral nerves. The general health may be impaired, and irritation of the pneumogastrics may be manifested by dyspepsia, nausea, vertigo, syncope, headache, dyspnoea, and inability to lie down. Laryngeal irritation is shown by cough, or spasm, with dryness of the throat; a frothy mucus may be expectorated, with occasional rigors, sweatings, and irregular febrile movement. When abscess follows severe injuries, such as fracture or wounds, distinct evidences of phlegmon appear, possibly within a week, accompanied by intermittent fever with rigors, and a sense of weight and oppression in the front of the chest, with pain in coughing and drinking, or breathlessness, "as if one had been running" (Petit).

The pressure symptoms of mediastinal abscess are never so grave as in other forms of mediastinal tumor, since the diffluent contents of an abscess occasion less compression of the mediastinal viscera, or when the intra-thoracic tension is excessive it seeks a channel by which the pus is evacuated. The pressure symptoms are least marked when the abscess is located in the anterior mediastinum.

There may be, on inspection, a distinct prominence over the upper part of the sternum, with or without redness or oedema. Palpation may enable one to recognize fluctuation on the borders of the sternum with tenderness. The tumor may pulsate, but the pulsation never acquires the expansile character of aneurism. Dulness on percussion may be marked, and, according to Daudé, the dulness under the sternum may undergo a change by alteration of the position of the patient. The heart sounds may be heard distantly and indistinctly. The respiratory murmur may be whistling over the region of the trachea, and in the chest a few moist râles may indicate venous congestion, with exudation into the bronchial passages; otherwise the condition of the lungs will probably be normal. The entire series of pressure symptoms common to intra-thoracic growths may be present, especially if the {863} posterior mediastinum is invaded, and may correspond with those of mediastinal tumors in general.

DURATION AND PROGNOSIS.--The causal relations of abscess in the mediastinum are so various that it is only possible to decide the question of duration after weighing the possibilities of treatment. The persistence of the abscess is also decidedly governed by the thoroughness of the drainage after opening has been affected.

The PROGNOSIS depends upon the etiology and the fulfilment of the indications for treatment by drainage. Pressure on the heart and the great vessels which proceed from its base, the descending aorta, oesophagus, the pneumogastrics, and the internal thoracic circulation, must be considered as complications adverse to a favorable prognosis unless speedy relief is possible. Prominent pressure symptoms indicate an implication of the intra-thoracic glandular system.

COMPLICATIONS, TERMINATION.--The abscess may open into any of the internal viscera--the trachea, bronchi, or oesophagus. A favorable case terminating by rupture into the latter passage is reported by Bennett. At first a teaspoonful of bright fluid blood was coughed up, and the day following from two to three ounces of purulent matter followed. The discharge of pus continued five weeks, the sternal swelling subsiding pari passu.

The pleura and pericardium have both been recorded as points of outlet. The pus can even sink down into the inguinal or lumbar region. Spontaneous external opening is said to occur most frequently on a level with the second rib to the left of the sternum.

DIAGNOSIS.--The differential diagnosis between abscess and other mediastinal growths will be considered in the section on Mediastinal Tumors.

TREATMENT.--The exploratory puncture is to be recommended if a fluctuating tumor appear presenting the general symptoms of abscess. Rest, local sedative applications, and the relief of pain are positive indications. Petit, Agnew, and others have applied the trephine to the sternum in search of pus, with a satisfactory result. It is, however, generally conceded that it is better to wait until pointing occurs, as the area of the sternum is so limited that in all probability matter forming behind it would speedily make its way to the surface in an intercostal space at one of the margins of the bone. If the abscess be deeper or due to scrofulous or syphilitic caries of the sternum, the matter which forms may escape into the neck or through perforations of the bone. The latter may be congenitally present or due to disease. Caries, necrosis, or fracture of the bone may make trephining obligatory, or the same indication may prevail if a dependent flow of pus sufficient to drain the cavity is not otherwise obtainable.[6]

[Footnote 6: Chassaignac, _Traité de la Suppuration_, tome ii. p. 330.]

A similar line of treatment would be indicated if there was no tendency to external pointing, and evacuation into the viscera seemed threatened.

Excision of the whole or part of the sternum for abscess, cancer, or other causes seems to have been fairly successful. Heyfelder[7] had collected, in 1863, 18 established cases, in which there were 17 recoveries and 1 death.

[Footnote 7: _Traité des Resections_, traduit de l'Allemand avec Additions et Notes, par le Docteur Boekels, Strasburg et Paris, 1863.]

Adhesions usually prevent a double pneumothorax, even when the sternum and ribs have been resected. Unilateral pneumothorax is not necessarily fatal.

Mediastinal Tumors.

ANATOMY.--The mediastinum is the space which the two pleural sacs leave between them in the antero-posterior plane of the chest, and which {864} contains all the thoracic viscera except the lungs. It is subdivided into three parts--the anterior, middle, and posterior mediastinum. A superior mediastinum has also been described. The space between the pleural sacs occupied by the heart enclosed in the pericardium, the vena cava superior, the ascending aorta, the pulmonary arteries and veins, the phrenic nerves with their accompanying arteries, and the bifurcation of the trachea and roots of the lungs with some bronchial glands, takes the name of the middle mediastinum.

The anterior mediastinum is narrow in the middle, where the edges of the lungs nearly meet, wider above, where the lungs diverge, and widest of all below, for the same reason. It is very shallow from before backward, and it is limited posteriorly by the anterior layer of the pericardium, in front by the sternum, with the fifth, sixth, and a small portion of the seventh costal cartilages, and by the triangularis sterni muscle. The region is occupied simply by connective tissue, save in its upper part, where lies, when it still persists, the shrivelled remnants of the thymus body. It also contains a few lymphatic glands and the left internal mammary artery and vein.

The superior mediastinum is bounded by a plane passing through the lower part of the body of the dorsal vertebra behind and the junction of the manubrium and the gladiolus in front. Its upper limit corresponds to the superior aperture of the thorax. The contents of this space are the transverse portion of the arch of the aorta and its three large branches, the trachea and oesophagus, the thoracic duct, the innominate veins, upper part of the superior vena cava, left recurrent laryngeal nerve, phrenic, pneumogastric, and cardiac nerves, with lymphatic glands and remains of the thymus body.

The posterior mediastinum is triangular in shape, placed in front of the lower border of the fourth dorsal vertebra downward, and bounded anteriorly by the pericardium and roots of the lungs. The lateral boundaries are formed by the pleuræ. The space contains the descending thoracic aorta: in front of the aorta the oesophagus with the pneumogastric nerves, the left in front, the right behind. On the right of the aorta is the vena azygos major; between this vein and the aorta is the thoracic duct; superiorly is the trachea; inferiorly are the splanchnic nerves and the posterior mediastinal lymphatic glands.

DEFINITION.--There are three principal forms of morbid growths in the mediastina--sarcoma, lymphoma or lymphadenoma, and carcinoma. Hyperplasia of the mediastinal glands also may arise, intertwined with various diseases, such as phthisis (especially the form known as pneumonic), pertussis, aneurism, rachitis, and syphilis. Enlargement of the lymphatic glands may occur in connection with the scrofulous diathesis, or similar enlargement associated with primary subacute or chronic bronchitis and the varieties of catarrhal fever and influenza.

Allusion in this place will only be made to the rare instances in which uncomplicated enlargement of the thoracic glands occurs in the mediastinal spaces. Aneurism, abscess, and pericardial effusions will be referred to only in so far as they affect differential diagnosis.

Mediastinal tumors, however, include certain forms which have the interest of pathological curiosities rather than possessing a clinical importance. Cysts in this region are rare, mostly of embryonic origin (dermoid), and contain epithelial structure, such as hair, sebaceous and sweat-glands, teeth, and occasionally bone, cartilage, and other tissues. These cysts often develop rapidly and may attain great size. Lipomata[8] occur as the result of an undue increase of the mediastinal fat, and are associated with accumulation of the same in the pericardium and in the system at large. Such tumors are rare and of very gradual development. Kronlein[9] has described a congenital lipoma of the {865} anterior mediastinum in a child aged one year, which found its way through an intercostal space and then rapidly increased in size. Fibromata, osteomata, and enchondroma are also possible mediastinal and pulmonary tumors, but are seldom met with. Exostoses may form upon the internal surface, and gummata upon the anterior and posterior surfaces of the sternum.

[Footnote 8: Reigel, _Virchow's Arch._, vol. xlix.]

[Footnote 9: Langenbeck, _Klinic_, p. 157.]

PATHOLOGY AND MORBID ANATOMY.--Pulmonary processes associated with bronchial catarrh frequently lead to enlargement of the bronchial glands, because, owing to the impervious character of the basement membrane of the bronchial passages, the mucous and epithelial portion of the exudation is expectorated, and that portion of the exudate which occurs from the bronchial blood-vessels is absorbed and carried by means of the pulmonary lymphatics to the bronchial glands. Tubercular deposits frequently occur in the glands of the posterior, and much less frequently in those of the anterior, mediastinum.

Independently of the above conditions, caseating bronchial glands have been found as complications of scarlatina with nephritis or tubercular meningitis. An interesting case of this condition has been reported as following an abscess in the glands at the root of the neck as a sequel to measles nine months before.[10] Riegel also mentions an instance in which some of the mediastinal glands were enlarged to the size of hen's eggs. The trachea was compressed at the point of bifurcation, so that its calibre was reduced to one-third its natural size. This case was free from other glandular enlargements. Coupland has described a case in a boy four years of age, in whom the cervical glands were enlarged and idiopathic hyperplasia of the bronchial glands was suspected. Autopsy: On raising the sternum a collection of indurated glands was found in the anterior mediastinum, and over the root of the right lung one of these glands had broken down into a cheesy mass. A chain of enlarged lymphatics accompanied the right bronchus. The largest caseous mass had ulcerated through the trachea just above the origin of the right bronchus by an aperture measuring half an inch along the axis of the tube, while for half an inch above its lumen was compressed. In this case the right lung was solidified and contained cheesy matter, with a cavity at the apex. The father of the child had also suffered from increase in the glandular tissues.

[Footnote 10: See _Path. Soc. London_, 1884.]

The historical literature of intra-thoracic morbid growths has been exhaustively reviewed in a monograph by Cockle, but until within the last fifteen years little attempt was made to separate mediastinal tumors into definite groups.

Our present knowledge on this subject was first shaped by Virchow,[11] since which period numerous cases have been recorded.

[Footnote 11: _Virchow's Archiv_, Bd. xciii. Heft 3.]

Sarcoma of the Mediastinum.--Primary sarcomatous growths are relatively uncommon. In 7566 cadavers examined at the Marine Hospital at Kronstadt there were found 158 malignant tumors, 127 being carcinomatous, the other 31 being sarcomatous. In 24 cases reported by Kahnlich, 13 occurred in the anterior mediastinal region, and a similar location was found in a case reported by the writer,[12] also in one instance reported by West.[13]

[Footnote 12: _Philada. Med. News_, March 15, 1884.]

[Footnote 13: _Path. Soc. London_, 1883.]

The anterior mediastinal space is a favorite location for the origin of the purely sarcomatous form of tumor. Sarcoma may arise from a persistent thymus (as in cases reported by Gee, Church, and Powell), from the parietal or visceral layers of the pericardium or pleura, from the periosteum of the sternum, or from the mediastinal connective tissue.[14]

[Footnote 14: Kahnlich, _loc. cit._, describes 13 as originating in the connective tissue of the anterior mediastinum, 5 in the periosteum of the sternum, and 1 in the pericardial substance.]

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In a disease of this rare nature we can best formulate an idea of the character of the growths by the recital of a few typical cases. In an autopsy made by the writer, on removing the sternum and cartilages they were found to be adherent on the right side to a mass which occupied the anterior mediastinum (see Fig. 53). The growth was seven inches long, measuring from the sternal notch, and terminated in a somewhat diffused thickening of the visceral pleura, which covered the anterior margin of the upper and middle lobe of the right lung. The growth was two and a half inches broad. It overlaid the aorta, pulmonary artery, and the vessels of the neck. The calibre of the trachea was slightly diminished. The glands of the neck were unaffected on either side. The posterior mediastinal glands were very slightly enlarged along the sides of the trachea and upper bronchi. Laterally, at the lower portion of the growth, the pulmonary pleura was thickened at the line of contact with the tumor, but the lungs were free from any traces of disease. The new formation was of fibrous consistence, of a gray-white color, and through its centre a softened tissue was found. Microscopic examination showed the growth to be composed of medium-sized lymphoid cells mixed with spindle-shaped cells, and imbedded in a homogeneous stroma or a stroma which consisted of reticulated fibres and wavy fibrous tissue. Other portions of the body were normal.

In West's case the tumor also occupied the anterior mediastinum, extending toward the second left intercostal space. The mass was about the size of a boy's head, soft, cellular, and adherent to the upper lobe of the left lung; it also rose into the episternal notch and left supra-clavicular fossa. The brachial plexus and vessels of the left side, subclavian and carotid arteries, the jugular and innominate veins, were imbedded in the tumor. The left bronchus and a portion of the trachea were flattened. The left phrenic and left pneumogastric nerves passed through the mass, and on dissection were found much thickened as they ran through the tumor. The tenth nerve measured {867} three times its normal diameter, and was pushed out of its course nearly an inch from the carotid. The recurrent laryngeal was also thickened; the right pneumogastric and phrenic nerves were not involved. The heart lay beneath the tumor; nodules of the new growth were found upon the anterior surface of the heart and along the vessels issuing from it. No secondary deposit was found in the lungs except at the margin of the left upper lobe, into which the tumor spread directly. The spleen, liver, kidneys, and lumbar glands were normal.

Microscopic examination determined the growth to be a round-celled sarcoma, the thickening of the nerves being due to infiltration by similar small-celled growth.

In primary sarcoma of the mediastinum--and the same is true of lymphadenoma--the invasion of the various intra-thoracic organs is chiefly by continuity or direct spreading of the growth. The lymphatics of the neck are very rarely implicated in this form of malignant disease; and while in lympho-sarcoma the glands may be involved, they are not so frequently as in cancerous processes. Sarcomata of the mediastinum with implication of the lungs and pleura are more frequently secondary processes; indeed, the lungs would seem never to be the seat of primary sarcoma. The pleural tissues, however, may be primarily involved. Lepine, Birch-Hirschfeld, Böhme, Eppinger, Schultz, Greenish, and others have reported cases in which the growths were abundantly distributed in the pleural tissues as primary formations. The point of origin is believed to be either directly from the ordinary connective-tissue cells or from the endothelium of the lymphatics.

Secondary sarcomata may form in the mediastinum or in the lungs within a month or so long as a year after the removal of tumors from other parts of the body, probably by metastasis prior to the removal. In some of these cases the seat of original growth and the neighboring glands may be entirely healthy.

In a typical case of multiple osteoid sarcoma of the lung reported by West fleshy vegetations were found on the visceral pleura: upon the parietal pleura, over the seventh rib, two inches from the spine and growing from it, was a lobular spongy mass as large as an orange, but perfectly disconnected with the parts beneath. The right lung was irregular in shape, owing to the presence of masses of new growth in its different parts. The middle lobe seemed almost completely converted into the new growth. Between the lower lobe and the diaphragm, but attached to the lung, was a mass the size of a cricket-ball, covered with a dark, laminated, but easily separated coagulum. The tumor occupied the upper lobe of the left lung, forming an irregular oval mass six by four and a half inches. It was white in color, and adherent to its upper border was compressed lung-tissue. There were also four or five independent nodules situated near the surface, and of a white color. The lower lobe contained one medium-sized growth and four or five small ones. The bronchial glands were not involved. The tumors appeared soft and spongy, but on incision they were found so hard that a knife could scarcely divide them.

Frequently, the lungs are found infiltrated with sarcomatous nodules of a soft consistency, varying in size from a walnut to an orange. To sum up: primary sarcomata may be the round- or spindle-celled variety; but myeloid sarcomata also occur, chiefly as secondary growths. (See Fig. 54.)

Lympho-sarcoma of the Mediastinum.--Lympho-sarcoma, lymphoma, or lymphadenoma is the form of malignant process which probably includes the majority of cases of primary mediastinal growth. It is sometimes, however, a part of a more general disease, affecting more or less the whole glandular system.