Idiopathic Fibrosis of the Mediastinum as a Cause of Superior Vena Cavai Syndrome

THE SUPERIOR vena cavai syndrome is a result of stenosis of the superior vena cava, which causes hypertension in the area it drains. The degree of the hypertension depends on the amount of stenosis, its position, and the rate of growth and capacity of the collateral circulation. Four main causes of stenosis are tumor, aneurysm, thrombosis, and mediastinitis. More uncommon are trauma, pericarditis with narrowing of the intrapericardial portion of the superior vena cava, pneumothorax, mediastinal emphysema, etc., and in some cases the cause is unknown. Statistics show that tumors predominate (3, 4, 11, 19) from 33 per cent (McIntire and Sykes, 11) to nearly 75 per cent (Bruckner, 3). Earlier reports showed aortic aneurysm to be the cause in 25 to 30 per cent of the cases (Mclntire and Sykes, 30 per cent), but recent publications show a much lower percentage—Calkins (4), 9 per cent and Bruckner, 4 per cent. Thrombosis may follow phlebitis with syphilitic, tuberculous, pyogenic, or traumatic etiology; or the thrombosis may be of unknown origin and registered as idiopathic thrombophlebitis. It is often secondary to compression of the superior vena cava. Mediastinitis is given as the cause of approximately 12 per cent of all cases of superior vena cavai syndrome (4). There has been much discussion of the reason for this diagnosis (2, 5, 11, 16). Some writers have suggested that a chronic mediastinal fibrosis is the usual result after tuberculous adenitis, syphilis, trauma, radiotherapy, etc. (11, 12). Others (2, 5) believe that in this group there is undoubtedly a clear, definite clinical picture without relation to the above-stated causes and with unknown etiology. Barrett uses the term idiopathic mediastinal fibrosis, comparing the condition with retroperitoneal fibrosis, pseudotumor in the orbit, and Riedel's struma, and proposes the theory of a relationship between these. Evidence of mediastinal fibrosis as a cause of superior vena cavai syndrome has consequences in treatment, for radiotherapy is then contraindicated as it stimulates fibrosis (2, 17). The main purpose of this paper is to call attention to this etiologic factor and also to the value of radiological examination with mediastinal phlebography (7–9, 13–15, 18) in diagnosis. More reliable information is thereby available when one is deciding on surgery or other forms of treatment. The technic in use at the Roentgen-Radium Department, Rikshospitalet, Oslo, in mediastinal phlebography is as follows : Following an incision to expose the basilic vein, a Lehmann catheter is inserted into the vein, the tip lying in the innominate vein or, if necessary, more distally. The contrast medium used is Isopaque 75 per cent, approximately 1 ml/kg body weight. Steinberg (18) warns against too strong a solution in suspected stenosis of the veins.