Chronic mediastinitis usually involves specific granulomatous processes with associated mediastinal fibrosis, chronic abscesses.
Histoplasmosis, tuberculosis, actinomycosis, nocardiosis, blastomycosis, and syphilis have been incriminated. Amebic abscesses and parasitic disease such as echinococcal cysts are rare causes. The infectious process is usually due to histoplasmosis or tuberculosis and involves the mediastinal lymph nodes. Esophageal obstructions may occur. Adjacent mediastinal structures may become secondarily infected. Granulomatous mediastinitis and fibrosing mediastinitis are different manifestations of the same disease. Mediastinal fibrosis is a term used synonymously with idiopathic, fibrous, collagenous, or sclerosing mediastinitis. Eighty or more cases of mediastinal fibrosis have been reported, but the cause has been determined in only 16%, and of these over 90% were due to histoplasmosis. In only 25% of 103 cases of granulomatous mediastinitis has the cause been identified. Histoplasmosis was the most common known cause (60%) and tuberculosis the second most common (25%).
About 85% of patients with mediastinal fibrosis have symptoms from entrapment of mediastinal structures as follows: superior vena caval obstruction in 82%; tracheobronchial obstruction, 9%; pulmonary vein obstruction, 6%; pulmonary artery occlusion, 6%; and esophageal obstruction, 3%. Rarely, inferior vena caval obstruction or involvement of the thoracic duct, atrium, recurrent laryngeal nerve, or stellate ganglion is found. Multiple structures may be simultaneously involved.
Seventy-five percent of patients with granulomatous chronic mediastinitis have no symptoms, and disease is discovered by chest x-ray, which shows a mediastinal mass. The mass is in the right paratracheal region in 75% of cases. In the 25% of patients with symptoms, about half have superior vena caval obstruction and one-third have esophageal obstruction. Occasional patients have bronchial obstruction, bronchoesophageal fistula, or pulmonary venous obstruction.
A mediastinal tuberculous or fungal abscess occasionally dissects long distances to present on the chest wall paravertebrally or parasternally. Secondary rib or costal cartilage infections with multiple draining sinus tracts occur.
Symptoms and Signs of Chronic mediastinitis
Granulomatous and fibrosing mediastinitis affects women two to three times more commonly than men. Women aged 20–30 years are most typically affected, though the disorder may present in the fourth to fifth decades. Esophageal involvement results in dysphagia or hematemesis. Tracheobronchial involvement may cause severe cough, hemoptysis, dyspnea, wheezing, and episodes of obstructive pneumonitis. Pulmonary vein obstruction—the most common serious manifestation—produces congestive heart failure resembling advanced mitral stenosis and is usually fatal. Although not diagnostic, the respective skin tests in cases due to histoplasmosis or tuberculosis are strongly positive.
X-ray findings demonstrate a right paratracheal or anterior mediastinal mass. There may be spotty or subcapsular calcifications. Classically, histoplasmosis presents with hilar node calcification or so-called “popcorn” granuloma appearance. Calcification can also occur in thymoma or teratoma located in the anterior mediastinum. Chest CT (with intravenous and oral contrast) is most effective in defining the extent of mediastinal fibrosis and impingement on vital structures.
Treatment of Chronic mediastinitis
Specific antimicrobial therapy is indicated when an infecting organism is identified. Patients with symptomatic mediastinal masses and fibrosis can require resection for relief of obstruction.
The prognosis following surgical excision of granulomatous mediastinal masses is good. Operative procedures do not appear to activate fibrosing mediastinitis, but success in treatment has been unpredictable. Most patients with fibrosing mediastinitis—whether treated or not—survive but have persistent symptoms.