**Superior Vena Cava Syndrome (SVCS)** is a **medical emergency** caused by **obstruction of blood flow through the superior vena cava (SVC)** — the major vein that drains blood from the head, neck, upper chest, and upper limbs into the heart.

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### 🧠 **Etiology (Causes):**

Most common cause:  
- **Malignancy (≈ 85%)**, especially:
  - **Lung cancer** (especially small cell)
  - **Non-Hodgkin lymphoma**
  - **Metastatic cancers (e.g., breast, testicular)**

Other causes:
- **Thrombosis** (especially from **central venous catheters or pacemaker wires**)
- **Fibrosing mediastinitis**
- **Aortic aneurysm or goiter compressing the SVC**

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### 🩺 **Clinical Features:**

Symptoms result from **impaired venous return** from the upper body:

- **Facial swelling or fullness**
- **Neck and upper limb swelling**
- **Distended veins** on chest wall or neck
- **Dyspnea**, cough, orthopnea
- **Headache, dizziness, visual disturbances**
- **Hoarseness** or **dysphagia** (due to local compression)
- **Stridor** (if airway is compressed)

Symptoms may be **worse when lying down**.

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### 🧪 **Diagnosis:**

- **Clinical suspicion** from history and exam
- **Chest X-ray**: may show mediastinal widening or mass
- **CT scan with contrast**: preferred imaging to confirm compression or thrombus
- **MRI or venography**: alternative if CT is contraindicated
- **Biopsy** if malignancy suspected

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### 💉 **Management:**

Depends on **underlying cause and severity**:

#### 🔹 Supportive:
- Elevate head of bed
- Oxygen
- Corticosteroids (if lymphoma suspected)
- Diuretics (to reduce edema)

#### 🔹 Specific:
- **Radiation therapy** (often first-line if malignant)
- **Chemotherapy** (especially in chemosensitive tumors like lymphoma)
- **Endovascular stenting** (rapid symptom relief)
- **Anticoagulation** if thrombosis

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### ⚠️ Emergency Features:
- Stridor
- Laryngeal edema
- Cerebral edema (confusion, decreased consciousness)

These warrant **urgent intervention**, potentially **airway management** and **stenting**.