Superior vena cava syndrome overview

# Overview
Superior vena cava syndrome (also known as SVCS), is a group of symptoms caused by obstruction of the superior vena cava. More than 60% of cases of superior vena cava obstruction are caused by malignant causes, typically a tumor outside the vessel compressing the vessel wall. However, in 20% of the cases, the cause is benign. Characteristic features are edema (swelling due to excess fluid) of the face and arms and development of swollen collateral veins on the front of the chest wall. Shortness of breath and coughing are quite common symptoms; difficulty swallowing is reported  in 11% of cases, headache in 6%, and stridor in 4%. The prognosis is generally poor and the survival rate of patients with superior vena cava syndrome is approximately 10-20% at 6 months. In less than 5% of cases of superior vena cava syndrome, severe neurological symptoms or airway compromise are reported. Treatment mainly consists of careful medical therapy (glucocorticoids) and surgery.

# Historical Perspective
Superior vena cava syndrome was first discovered by William Hunter (1718-1783), a Scottish obstetrician, in 1757.

# Pathophysiology
Superior vena cava syndrome arises from the obstruction of venous blood drainage of the superior vena cava, which is normally involved in the major blood flow return from head, neck, upper extremities, and upper thorax to the heart. Superior vena cava syndrome is a complication of a partial or complete obstruction due to malignant causes (60%) or benign causes (20%). This syndrome consists on the invasion of the venous wall associated with intravascular thrombosis, enlarged nodes, enlarged ascending aorta,  or by extrinsic pressure of a tumor mass against the thin-walled superior vena cava  which leads to the development of superior vena cava syndrome. Superior vena cava syndrome is associated with a number of conditions that include malignant tumors, tuberculosis, histoplasmosis, and syphilis.

# Causes
Superior vena cava syndrome may be caused by obstruction of the superior vena cava by neoplastic invasion of the venous wall, intravascular thrombosis, enlarged lymph nodes, enlarged ascending aorta, or by extrinsic pressure of a tumor against the thin-walled superior vena cava.

# Differentiating Superior Vena Cava Syndrome from other Diseases
Superior vena cava syndrome should be differentiated from other causes of dyspnea and jugular venous distention, such as, cardiac tamponade, chronic obstructive pulmonary disease, mediastinitis, pneumonia, acute respiratory distress syndrome, and syphilis.

# Epidemiology and Demographics
Superior vena cava syndrome is a common oncologic emergency. The incidence rate in the United States is approximately 15,000 individuals each year. The incidence of superior vena cava syndrome increases with age; the median age of diagnosis is between 40-60 years. Males are more commonly affected with superior vena cava syndrome than females.

# Risk Factors
The most potent risk factor in the development of superior vena cava syndrome is intrathoracic malignancies. Other common risk factors include thrombosis (due to intravascular devices), postradiation fibrosis, and mediastinitis.

# Screening
According to the the National Cancer Institute, there is insufficient evidence to recommend routine screening for superior vena cava syndrome.

# Natural History, Complications and Prognosis
If left untreated, patients with superior vena cava syndrome may progress to develop a complete blood flow obstruction and a decreased cardiac output with hypotension, leading to heart failure and death. Common complications of superior vena cava syndrome include airway obstruction, increased ICP, laryngeal edema, and cerebral edema. The prognosis will vary depending on the cause of the syndrome, and the amount of blockage that has already occurred. Prognosis is generally poor and the survival rate of patients with superior vena cava syndrome is approximately 10-20% at 6 months.

# Diagnosis

## Staging
According to the Journal of Thoracic Oncology, there are 5 stages of superior vena cava syndrome based on the severity and incidence. Each stage is assigned a grade and a description that designate disease severity.

## History and Symptoms
The hallmark of superior vena cava syndrome is elevated jugular venous pressure. A positive history of cancer and intra-vascular devices are suggestive of superior vena cava syndrome. The most common symptoms of superior vena cava syndrome include upper body swelling, dyspnea, and cough.

## Physical Examination
Common physical examination findings of superior vena cava syndrome include the pemberton's sign, facial swelling, and jugular venous distension.

## Laboratory findings
There are no diagnostic laboratory findings associated with superior vena cava syndrome.

## Chest X Ray
On chest x-ray, indirect signs such as superior mediastinal widening and right hilar prominence may indicate the presence of a mediastinal mass.

## CT
On enhanced CT scan, findings include location and severity of the superior vena cava obstruction, superimposed thrombosis, a mediastinal mass or lymphadenopathy, collateral vessels, and associated lung masses. CT scan is the imaging modality of choice.

## MRI
MRI may be helful to provide images without the use of contrast (useful in patients with renal failure).

## Ultrasound
Doppler ultrasound may be valuable in assessing the site and nature of the obstruction in superior vena cava syndrome. Venous patency and the presence of thrombi can also be assessed by using contrast and rapid scanning techniques.

## Other Imaging Findings
Other imaging finding is the radionuclide technetium-99m venography.

## Other Diagnostic Studies
Other diagnostic studies in the evaluation of superior vena cava syndrome include sputum tests, bronchoscopy, and biopsy. In addition, invasive contrast venography is also a diagnostic tool in the diagnosis of superior vena cava syndrome. It may be useful on the etiology of obstruction and exact location of the obstruction, also helpful in the surgical management of the obstructed vena cava.

# Treatment

## Medical Therapy
Superior vena cava syndrome is a medical emergency and requires prompt treatment. The treatment of superior vena cava syndrome depends on the etiology of the obstruction, the severity of the symptoms, the prognosis of the patient, patient preferences, and goals for therapy.

## Surgery
Elective stent placement and surgical bypass is recommended for all patients who develop superior vena cava syndrome.

## Radiation Therapy
Rapid radiotherapy is recommended for all patients who develop superior vena cava syndrome secondary to malignant tumor. The feasibility of radiation therapy depends on the stage of cancer at diagnosis. Radiation dosage will depend on clinical features.

## Primary Prevention
There are no primary preventive measures available for superior vena cava syndrome.