Deflection
of Mediastinum
In the cadaver, the mediastinum, as the result of the
hardening effect of the preserving fluids, is an inflexible, fixed structure.
In the living, it is very mobile; the lungs, heart, and large arteries are in
rhythmic pulsation, and the esophagus distends as each bolus of food passes
through it.
If air enters the pleural cavity (a condition called pneumothorax),
the lung on that side immediately collapses and the mediastinum is displaced to
the opposite side. This condition reveals itself by the patient’s being
breathless and in a state of shock; on examination, the trachea and the heart
are found to be displaced to the opposite side
Mediastinitis
The structures that make up the mediastinum are embedded in loose
connective tissue that is continuous with that of the root of the neck. Thus,
it is possible for a deep infection of the neck to spread readily into the
thorax, producing a mediastinitis. Penetrating wounds of the chest involving
the esophagus may produce a mediastinitis. In esophageal perforations, air
escapes into the connective tissue spaces and ascends beneath the fascia to the
root of the neck, producing subcutaneous
emphysema.
Mediastinal
Tumors or Cysts
Because many vital structures are crowded together within the
mediastinum, their functions can be interfered with by an enlarging tumor or
organ. A tumor of the left lung can rapidly spread to involve the mediastinal
lymph nodes, which on enlargement may compress the left recurrent laryngeal
nerve, producing paralysis of the left vocal fold. An expanding cyst or tumor
can partially occlude the superior vena cava, causing severe congestion of the
veins of the upper part of the body. Other pressure effects can be seen on the
sympathetic trunks, phrenic nerves, and sometimes the trachea, main bronchi,
and esophagus.
Mediastinoscopy
Mediastinoscopy is a diagnostic procedure whereby specimens of
tracheobronchial lymph nodes are obtained without opening the pleural cavities.
A small incision is made in the midline in the neck just above the suprasternal
notch, and the superior mediastinum is explored down to the region of the bifurcation
of the trachea. The procedure can be used to determine the diagnosis and degree
of spread of carcinoma of the bronchus
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