Galen has alluded to trephining of the sternum for caries or necrosis inducing the formation of pus; and Petit1 has furnished many instances of mediastinal abscess from the warfare of preceding centuries.
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.
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
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.
Warner4 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.