notes by dr Claudio Italiano
Anatomical references.
The mediastinum is the part of the thoracic space between the two pleural cavities delimited anteriorly from the sternum, posteriorly from the vertebral column (I-XI thoracic vertberba), on the sides from the mediastinal pleurae, superiorly communicates directly with the cervical fascias through the upper thoracic strait and inferiorly it is delimited by the diaphragm. The mediastinum can be divided into three compartments (anterosuperior, middle, posterior mediastinum) and this subdivision is useful for the topographic and diagnostic classification of mediastinal neoformations. In the anterosuperior mediastinum are contained: the thymus, the lymph nodes, supporting connective tissue and internal mammary vessels.
In the middle mediastinum are pericardium, heart and large vessels (see upper cava, v. Anonymous, aortic arch and its branches), n. frenici and n. vague (upper portion), trachea and ili pulmonari, lymph nodes and supporting connective tissue. In the posterior mediastinum are contained: thoracic duct, v. azygos and emiazygos, descending aorta, sympathetic chains and n. vague (lower portion), lymph nodes and connective areolar. Mediastinitis, ie inflammatory processes of the mediastinum, may have an acute or chronic course, be diffuse or circumscribed, recognize various etiologies, among which once prevailed the tubercular and the syphilitic, while the most frequent causes are currently represented by streptococci , staphylococci, pneumococci and Escherichia coli. They are localizations to the mediastinum of infections primitively established in other districts in relations of contiguity with the mediastinal space (osteomyelitis of the sternum or dorsal vertebrae, mediastinal pleuritis, thymus abscesses, bacterial bronchopneumonia, suppuration and rupture of a cyst, esophageal fistulae, perforated esophageal diverticula) or distant (typhoid infection, otitis, erysipelas, scarlet fever, etc.). Even gunshot and cutting wounds can be the entrance door for germs capable of originating a mediastinal infection. If we ignore the luetic and tuberculous forms, now completely extinct, the other bacterial mediastinites may present in diffuse form (mediastinitis, phlegmonous) or circumscribed (mediastinal abscess).
We distinguish:
Acute mediastinitis:
a) esophageal perforation
b) bronchial perforation
c) spread of infections contiguous to the mediastinum or by blood
Chronic mediastinitis:
a) granulomatous forms such as tuberculosis, histoplasmosis, nocardiosis
b) fibrotic forms, infectious granulomatous processes
Apart from the symptoms and signs correlable with the main infectious outbreak that started the mediastinitis, this, when it is clearly constituted, manifests itself with a general symptomatology (intermittent or remitting fever, rapid impairment of the general state, sense of deep prostration, intense sweating in coincidence of the fall of temperature, cough, dyspnea) and local represented by the appearance of a deep, pulsating thoracic pain, localized by the patient to the retrosternal or interscapular region, by the appreciation of a more or less edematous infiltration diffuse or circumscribed, detectable at the neck and the chest wall, from living painfulness to the pressure of the sternum, or, depending on the location of the purulent collection, on the spinous apophysis of the dorsal vertebrae. Further elements in favor of the presence of an inflammatory process of the mediastinum are the dysphagia, the irritation of the phrenic or the vagus with the related symptoms, provided that they are inserted in the context of a clinical picture in other ways indicative of a similar hypothesis. In the acute mediastinitis the radiological survey does not produce useful indications; only in the ascissualized forms his contributions are decisive and decisive. The prognosis depends on the possibility of acting on the infectious cause that is at the origin of mediastinal inflammation. The therapy is medically, but above all surgical. In any case, the intervention must be supplemented by the pre-intra- and post-operative antibiotic treatment. The chronic mediastinites that were once dominated by the luetic or tubercular etiology have now almost disappeared from the clinical scene, so it is sufficient to have just mentioned it.