Superior Vana Caval Syndrome

Superior Vena Caval Syndrome (SVCS) results from a space occupying lesion (SOL) in the superior mediastinum. The presence of a SOL results in compression of structures passing through the mediastinum. The most prominent clinical manifestations result from compression of superior vena cava and for this reason it is also referred as superior vena caval syndrome. Superior mediastinal syndrome,  a term that captures the pathogenesis of the syndrome, is also used. SVCS was first described by William Hunter in 1757 in a patient with syphilitic aortic aneurysm. Today the most common cause is a malignancy.

Anatomy of the Superior Mediastinum

Superior mediastinum is bound

1. Inferiority by an imaginary plane running from the sternal  angle to the fourth thoracic vertebra,
2. Superiority by the thoracic inlet
3. Anterior by manubrium of the sternum
4. Posteriorly by the bodies of first four thoracic vertibrae.
5. Laterally by the pleura.

It is space through which tubular structures pass from the neck to the thoracic organs. These include the following

1. Arch of the aorta and its branches including Brachiocephalic artery, Left Common carotid artery, Left Subclavian artery – to the left upper limb.
2. Superior Vena Cava and its tributaries Brachiocephalic veins, Left superior intercostal vein, Supreme intercostal vein, Azygos vein
3. Lymph nodes draining the lung are found in the fatty tissues.
4. Oesophagus

Pathogenesis of SVCS

Superior mediastinum has rigid walls, making the structures passing through it prone to compression by mass lesions. The commonest cause of compression is a malignancy arising from or involving structures of superior mediastinum. Lung cancer and lymphoma being the two commonest causes of SVCS. Some conditions like Mediastinal fibrosis may constrict rather than compress the mediastinum. Indwelling vascular lines has increased the risk of thrombosis of superior vena cava common. One needs to consider the possibility of thrombosis in patients who have indwelling venous access devices.  The table lists the causes of superior vena caval syndrome.

Malignant	Non-Malignant
Lung cancer Lymphoma Others: metastatic cancers, primary leiomyosarcomas of the mediastinal vessels, plasmocytomas	Mediastinal fibrosis Vascular diseases, such as aortic aneurysm, vasculitis, and arteriovenous fistulas Infections, such as histoplasmosis, tuberculosis, syphilis, and actinomycosis Benign mediastinal tumors such as teratoma, cystic hygroma, thymoma, and dermoid cyst Cardiac causes, such as pericarditis and atrial myxoma Thrombosis related to the presence of central vein catheters

Manifestations

The common manifestations of superior vena cava syndrome include

1. Dyspepsia
2. Swelling of the face and upper extremities
3. Cough, chest pain
4. Dysphagia

Examination shows distended neck veins and chest wall oedema, plethora of face, and oedema of the arms.

Diagnosis

Radiology: Radiograph of chest usually shows a mediastinal mass. If not this is apparent of on a CT scan. The CT scan is also needed to define extent of disease and invasion of the great vessels, bronchus, and the spinal cord.

Biopsy and Cytology: The investigations to establish diagnosis include sputum cytology, examination of pleural fluid (if present) and histology. The tissue for histological examination may be obtained by bronchoscopy, thoracoscopy, mediastinoscopy guided lymph node biopsy, CT guided core needle biopsy of the mass. A bone marrow examination may be of value if the haemogram is abnormal. A careful examination of the supraclavicular region shows nodes in about 2/3^rd of the patients with SVCS which can be biopsied.

Treatment

The aim of treatment of SVCS is to relive symptoms at the same time not compromise diagnosis or the possibility of cure. All patients should be given head elevation and oxygen. Diuretics can reduce oedema but this comes at the cost of dehydration. Tissue must be obtained for diagnosis. Unless there has been a substantial delay in diagnosis, initiation of treatment is not an emergency and tissue can be obtained. Vascular stents can be inserted in patients who are very symptomatic to relieve symptoms till diagnosis is made. 

The treatment of SVCS is disease specific. Chemotherapy with or without radiation is indicated in patients with lung cancer (small cell as well as non-small cell). The response rate in small-cell lung cancer exceeds 90% with 70% of the patients remaining disease free. Addition of radiation to chemotherapy reduces the risk of recurrence. About 60% of the patients with non-amall cell lung cancer respond to therapy. The disease recurs in about 20% of these. Patients with NSCLS presenting with SVCS have a poorer survival than those who do not. Lymphoma is treated with chemotherapy. 

Catheter-induced SVCS may be treated with thrombolytic agents early (< 5 days) in the course of the disease. Catheters of patients with prolonged symptoms should be removed and this should be done under cover of heparin.

Patients who have cancers that do not respond to chemotherapy or radiation can be palliated by placement of vascular and tracheal stents where possible.