Mediastinum is a space between the pleural cavities. Laterally, there are mediastinal pleurae. Sternum forms the anterior border; spine stands posteriorly and diaphragm limits the space caudally. There is no anatomical structure cranially, however, and cervical space infections can descend easily into mediastinum. The space is divided into superior mediastinum (above the pericardium) and inferior mediastinum (between the superior border of pericardium and the diaphragm). The latter is further subdivided into anterior, middle and posterior spaces. For clinical purposes, also superior mediastinum is subdivided into anterior, middle and posterior.

In the posterior mediastinum, there is esophagus and membranous part of trachea close to it. In the upper mediastinum and on the left of esophagus, there is aortic arch with its branches (innominate artery or brachio-cephalic trunk, left common carotid artery, left subclavian artery), superior vena cava, innominate (brachiocephalic) veins, azygos vein, superior intercostal veins, vagal nerves, left recurrent nerve, phrenic nerves and thymus. Anterior mediastinum contains lymphatic and adipose tissue, connective tissue and sometimes a part of thymus. There is heart and its large vessel run-offs, tracheal bifurcation, main bronchi, phrenic nerves, pericardio-phrenic vessels and lymph nodes. Posterior mediastinum incorporates middle and distal esophagus, thoracic aorta, thoracic duct, splanchnic nerves, vagal nerves, azygos and hemiazygos veins, posterior intercostal arteries and lymph nodes.

Diagnostic tools

Non-invasive methods include plain chest x-ray and CT scan, the two basic ones. Other imaging methods include MRI, PET/CT, radionuclide angiography, radionuclide lympho-scintigraphy. Invasive techniques transparietal puncture biopsy (CT or ultrasound guided), transbronchial puncture biopsy (with EBUS), mediastinoscopy, extended mediastinoscopy, anterior mediastinotomy (Chamberlain procedure), sternotomy (partial or complete), parasternal mediastinotomy, posterior paravertebral mediastinotomy, transcervical extended mediastinal lymphadenectomy (TEMLA), video-assisted mediastinal lymphadenectomy (VAMLA), video-assisted thoracic surgery (VATS), anterolateral or posterolateral thoracotomy, transhiatal laparoscopic approach.

Mediastinal disease

Acute mediastinitis is a serious disease with high mortality, especially if left untreated. Before the antibiotic era, septic head, neck, pleural space or peritoneal space infections represented major part of etiologies. Nowadays, esophageal perforation is the most common cause. Anaerobic bacteria are frequently involved. The infection spreads quickly through mediastinal connective tissue, the space being unable to localize the process. Acute mediastinitis presents with non-specific serious illness symptoms and signs, fever, tachycardia, sepsis and septic shock. Also, retrosternal pressure pain, dyspnea, cough, filled neck veins, subcutaneous emphysema, fluido-pneumothorax, hematemesis.

Diagnostics is carried out with oral contrast CT scan or bronchoscopy to exclude perforation of the esophagus and tracheo-bronchial tree respectively. Laboratory tests are also performed. Therapy consists in the treatment of sepsis, antibiotics, drainage of fluid collections. Original source of infection must be addressed as well. Esophageal perforation is delt with by direct suture or subtotal resection with esophagostomy and feeding jejunostomy or gastrostomy. Gastroplasty for reconnecting of gastrointestinal tract is usually postponed. ENT focus is treated by corresponding specialists. 

Mediastinal abscess

Inflammatory process may sometimes result in localized collection of pus and detritus. Therapy is similar to mediastinitis, some cases are possibly drained under CT guidance.

Chronic mediastinitis

Chronic fibrosing mediastinitis is caused by infection (TB, actinomycosis, histoplasmosis, syphilis, encased foreign bodies), other external influences (radiation, sarcoidosis, silicosis) or it may be idiopathic. Compression of mediastinal structures occurs, presenting as stridor, cough and/or superior vena cava syndrome. It is treated causally in case of infection, otherwise symptomatically. Corticosteroids are used in some cases.

Mediastinal tumors

A wide range of tumors of completely different behavior arise in mediastinum. We list one of the possible sorting (Wychulis 1971). Others, like Diviš classification, are used. Neurogenic tumors, thymomas, benign cysts, lymphomas, granulomas, teratomas, intrathoracic goiter, mesenchymal tumors, primary carcinomas, mixed tumors.

Tumors can be asymptomatic or present by compression of the surrounding structures producing dysphagia, dyspnea, stridor, superior vena cava syndrome, lung atelectasis and pneumonia, lung congestion, hemoptysis, intercostal neuralgia, diaphragm paresis, Horner syndrome, dyspeptic problems. Thymomas may cause myasthenia gravis. Diagnosis is made with CT or MRI scanning. The most appropriate way of obtaining biopsy specimens should be determined according to the position of the tumor. EBUS, videomediastinoscopy or VATS are usually used (see methods above for more details).

Neurogenic tumors are the most common. They arise from sympathetic or intercostal nerves. They can be both benign or malignant and are located in the posterior mediastinum. The treatment is surgical.

Thymomas are in the anterior mediastinum. They can also be both benign and malignant. A thymectomy is performed. Malignant cases also undergo radiotherapy.

Teratomas are found mainly in the anterior mediastinum. Dermoid cyst is a typical representative. Mature teratomas are well differentiated, congenital, benign tumors formed from pluripotent embryonic germ cells. Some of these tumors can occur extragonadally, most often in the anterior mediastinum. Germ cell tumors can be benign and malignant. Benign tumors can be primarily solid (teratomas and dermoids) or cystic (epidermoid and dermoid). Malignant tumors further subdivide into seminomas and non-seminomas. Non-seminomas include malignant teratomas, embryonic carcinomas, choriocarcinomas, myxoid tumors, teratocarcinomas and yolk sac tumors.

Lymphomas and other haemato-oncological malignancies either arise in mediastinum or spread to it from different location. The disease process predilects in peribronchial and anterior mediastinal lymph nodes. This group of pathology warrants non-surgical treatment (chemotherapy)

Other tumors are cancers, mesenchymal tumors (lipoma, fibroma, chondroma, rhabdomyoma, leiomyoma, myxoma, hemangioma, xanthoma) are benign or malignant (sarcomas). Treatment is surgical. Furthermore, retrosternal goiters and adenomas of parathyroid glands. Mediastinal lymph nodes can also be affected by the metastatic process. Mediastinal pseudotumors are of differential diagnostic significance.