From Abscess.—The etiological relation in this process is traumatic, or mediastinal abscess occurs in connection with caries or fracture or after an operation in the neighborhood of the throat or neck, or of suppurative disease elsewhere in the thorax, as abscess of the lung or empyema. The pain in cases of abscess is deep-seated, constant, slowly increasing, rather than the paroxysmal pain of aneurism or solid tumor. The febrile movement may afford decided aid in the diagnosis, but it is also true that high temperature may mark the progress of lymphadenomata, as in Bennett and Sutton's case, in which from Jan. 11th to Feb. 28th the thermometrical wave vibrated between 103.5° maximum, with a pulse of 148 per minute, to 100.5° minimum, with a pulse of 108. In this remarkable case sweating was also a prominent feature; and a somewhat similar example has been recorded by Murchison. In corresponding circumstances the existence of secondary processes in the lungs or elsewhere, with enlarged glands in the neck, may prevent error. In mediastinal abscess there will probably be a tendency to point, with the appearance of a fluctuating, circumscribed, superficial tumor at the sternal border or adjacent to this bone. There may also be tenderness on pressure associated with the pain, and an oedematous condition of the tissues of that portion of the sternal region covering the tumor, although this symptom sometimes attends malignant new formations. Pulsation may accompany abscess, but will be of the transmitted variety. In suspicious cases the sternal bone can be drilled and an exploratory needle introduced into the tumor.
The general diagnosis of mediastinal tumor can be more easily made upon the basis of regional invasion. But in any suspicious case an elaborate and thorough clinical history is an essential prerequisite. In proportion as one completes the natural history of a case of obscure intra-thoracic disease the more likely one is to approach by exclusion a correct interpretation of the existing physical signs and symptoms.
Growths in the Anterior Mediastinum.—Tumors located in the anterior mediastinal space overlie the heart and aorta, and consequently the heart-sounds, especially the second, may be indistinct or muffled; or the second sounds may be audible in some new situation, owing to displacement of the heart. The sternal region may be distinctly prominent or bulged, and at the notch the bone may appear thickened. The resonance in the interscapular regions remains unimpaired, but over the sternum percussion should yield a very dull sound if the growth be large, but when a comparatively small tumor exists the sternal resonance will be hardened and high-pitched. An additional explanation of this modification exists in instances where the growth is not adherent to the sternum and the bone is arched over the tumor.
The respiration may be whistling or stridulous if the stethoscope is placed over the trachea, and over one or other apex anteriorly the respiratory murmur may be feeble or blowing, in proportion to the volume of air which is permitted to enter the chest. Posteriorly, the respiratory murmur may be unaffected at first, although as the growth advances evidence of pressure on the bronchial tubes may be detected over the interscapular region. The superficial veins of the chest may be enlarged, especially those below the level of the upper segment of the sternum. Dysphagia is usually slight in proportion to the other pressure symptoms or entirely absent. It may be simply a symptom of irritation of the intra-thoracic nerves or due to enlargement of the glands of the mediastinum.
Mediastinal growths usually develop in the middle line; they spread in all directions, especially laterally, but avoid at first the roots of the lungs. Pressure is rather exercised upon the parts in the mesial line. They reach a large size and grow with great rapidity, producing symptoms rather as a consequence of their size than by virtue of contractile properties.
From Pericarditis.—A possible pericarditis may be mistaken for a tumor of the anterior mediastinum. The diagnosis of pericarditis must be sustained by evidence showing the dependence of this process upon rheumatism, syphilis, nephritis, or propagated inflammation. The distension of the pericardial sac due to pericarditis exhibits a definite outline. The dulness of a tumor is irregular, with a tier of dulness upon a higher level than in effusion. The absence of various pressure signs is marked in pericarditis, while disturbance of the heart's rhythm is more frequent. Kussmaul states that there are two signs characteristic of chronic pericardial inflammation with thickening and adhesion—viz.: a "complete or almost complete failure of the radial pulse during inspiration, and simultaneously visible swelling of the great veins of the neck, instead of the collapse that usually takes place during this portion of the expiratory act. Adhesion of the great vessels to the sternum, either directly or through the medium of the pericardium, is supposed to account for these phenomena."
Febrile movement is usually present in pericarditis, and, while a possible temporary feature in new growths, is not persistent unless complicated by inflammation in the pulmonary tissues. Finally, the progress of the case will often decide the question.
Growths in the Posterior Mediastinum.—In growths located in the posterior mediastinum one or the other bronchus is one of the earliest structures implicated by the pressure, because in these cases the chief mass of tumor is found at the root of the lung. Secondary lesions in the lungs directly traceable to pressure are frequent, but unilateral, although secondary cancer from malignant lesions elsewhere than in the lungs may be bilateral. Pressure symptoms as a class occur early, are grave, constant, and progressive. Percussion according to directions of Guéneau de Mussy may be made available. Abolition or great impairment of breath and voice sounds over one or other posterior aspect of the chest is the rule, since these tumors are prone to contraction. Sometimes the respiratory murmur is whistling or blowing if the bronchial pressure is less decided. Progressive emaciation and cachexia are commonly present, not only from the inherent tendencies of the disease, but also depending upon the disturbance of the functions of many important organs which have been encroached upon by the tumor. The exclusion of a malignant disease of the oesophagus is very difficult. The passage of a bougie might determine the seat of obstruction, and thus assist in the diagnosis, but great caution must be observed lest penetration of the softened tissues occur. (See Cancer of Oesophagus.)
From Pleural Effusion.—The greatest difficulty may be experienced in deciding between uncomplicated pleurisy and effusion complicated by morbid growth.
Aside from the history of the case and state of nutrition, paracentesis may aid the diagnosis, since, if the fluid is turbid, highly albuminous, with a large proportion of coagulable fibrin, it is an evidence of inflammatory origin; but if it is clear, limpid, and on standing gives but a delicate veil of pseudo-fibrin, it indicates a passive or mechanical cause. Hemorrhagic exudation is only of relative importance. The recognition of pleural friction râles over parts flat on percussion will be an evidence of tumor. Hæmoptysis in this association would negative the idea of simple effusion. The presence of signs of pressure on central parts is indicative of tumor (Walsh), but Powell has recorded an instance of simple pleural effusion accompanied by husky voice and laryngeal cough; and also an instance in which, from a similar cause, there was increased size, tortuosity, and throbbing of the radial and brachial arteries on the affected side without oedema of the limb, yet probably attributable to obstruction of the return circulation.