superior vena cava syndrome

**Definition:** Impaired venous return from the head, neck, upper extremities, and upper thorax due to extrinsic compression, invasion, or intraluminal thrombosis of the SVC.

**Anatomy/Pathophysiology:** The SVC is a thin-walled, low-pressure vessel in the middle mediastinum, surrounded by rigid structures (sternum, trachea, right mainstem bronchus, aorta, pulmonary artery) and lymph nodes (right paratracheal chain). It is easily compressed by right-sided masses or enlarged nodes. Obstruction raises venous pressure upstream, causing edema and development of collateral circulation (azygos system, internal thoracic, lateral thoracic, and paraspinal veins). Gradual onset allows collateral development; acute onset is more symptomatic.

**Etiology:** - Malignancy (~60-85% in classic teaching): non-small cell lung cancer (most common overall), small cell lung cancer (highest rate per case), non-Hodgkin lymphoma (esp. diffuse large B-cell, lymphoblastic), thymoma, germ cell tumors, metastatic breast cancer. - Benign/iatrogenic (increasing, now a large share): thrombosis from central venous catheters, pacemaker/ICD leads, dialysis catheters; hypercoagulable states. - Other: fibrosing mediastinitis (histoplasmosis), tuberculosis, aortic aneurysm, goiter, syphilitic aortitis (historical), constrictive pericarditis.

**Clinical features:** - Facial, neck, and upper extremity swelling/plethora (worse when bending forward or lying supine) - Dilated neck and chest wall veins; JVD - Dyspnea, cough, hoarseness, stridor - Headache, dizziness, visual changes, syncope - **Pemberton sign:** facial plethora, JVD, and inspiratory stridor when raising arms above the head for ~1 minute - Severe cases: cerebral edema (altered mental status) or laryngeal edema (airway compromise) - Distinguish from Pancoast tumor (apical lung tumor; Horner syndrome, shoulder/arm pain, ulnar nerve distribution symptoms) and cardiac tamponade.

**Diagnosis:** Chest X-ray (mediastinal widening, right hilar mass, pleural effusion) is often the first test. Contrast-enhanced CT chest is the best initial imaging for diagnosis and for determining the cause and extent. Venography is the gold standard for the anatomic assessment (often at time of stenting). Obtain tissue diagnosis (biopsy) before starting radiation/steroids when possible, especially if lymphoma is suspected, as treatment can obscure histology.

**Management:** - Supportive: elevate head of bed, oxygen; diuretics and steroids have limited evidence (steroids helpful in lymphoma/thymoma). - Endovascular stenting: fastest symptom relief; first-line for severe symptoms (stridor, cerebral edema) or when rapid relief is needed. - Definitive treatment of the underlying cause: chemotherapy (SCLC, lymphoma, germ cell tumors are chemosensitive), radiation therapy (NSCLC and others). - Thrombotic SVC syndrome: anticoagulation, +/- catheter removal, thrombolysis/thrombectomy. - Note: SVC syndrome is no longer considered an absolute emergency unless there's airway obstruction (stridor) or severe cerebral edema; establish a tissue diagnosis first when the patient is stable.

**Boards pearls:** - Classic vignette: smoker with a right hilar/paratracheal mass, facial swelling, and distended neck veins; think lung cancer (SCLC/NSCLC) or lymphoma. - Young patient with anterior mediastinal mass: think the four T's (thymoma, teratoma/germ cell tumor, thyroid, terrible lymphoma). - Complications of SVC syndrome include cerebral edema, airway obstruction, and thrombosis. - Differentiate from IVC obstruction (lower extremity edema, ascites, Budd-Chiari if hepatic veins involved).