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Mediastinal Diseases

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Mediastinal diseases refer to a wide range of conditions that affect the structures within the mediastinum, the central compartment of the chest located between the lungs. This area contains vital organs such as the heart, major blood vessels, lymph nodes, and the trachea. Possible causes of mediastinal diseases include lymph node enlargement (caused by infections, inflammation, autoimmune diseases, or malignancies), thymoma, abscess, malignant tumors, aortic aneurysm or esophageal disorders.

Symptoms

The symptoms of mediastinal diseases depend on the nature and location of the lesion. Common symptoms include:

Respiratory Symptoms
- Cough, Difficulty Breathing, or Stridor:** Often caused by compression of the trachea or bronchi.
- Chest Tightness: When tumours or vascular lesions compress the lungs.
Chest Pain
- Localized or radiating chest pain, potentially associated with infections, tumours, or aortic aneurysms.
Difficulty Swallowing (Dysphagia)
- Occurs when the lesion compresses the oesophagus, causing pain or difficulty swallowing.
Hoarseness
- Caused by recurrent laryngeal nerve compression, commonly seen in thymomas or tumour-related lymphadenopathy.
Superior Vena Cava Syndrome
- Swelling of the face, neck, or upper limbs, accompanied by distended veins, often due to tumour compression of the superior vena cava.
Systemic Symptoms
- Fever, Weight Loss, and Night Sweats:** Frequently observed in patients with infections or malignant tumours.

Causes and Factors

Mediastinal diseases are diverse in origin and are typically associated with the following factors:

Infectious Causes	Pulmonary Tuberculosis: Common in Hong Kong, often leading to mediastinal lymph node enlargement. Viral Infections: Epstein-Barr Virus (EBV) can cause lymph node enlargement. Bacterial Abscesses: Secondary infections caused by thoracic infections or oesophageal perforation.
Tumour-Related Lesions	Benign Tumours: Including teratomas, neurogenic tumours, and lipomas. Malignant Tumours: Thymomas: One of the most common mediastinal tumours, strongly associated with myasthenia gravis. Germ Cell Tumours: These include seminomas and non-syringomatous germ cell tumours, often seen in young males. Metastatic Tumours: Such as lung cancer or breast cancer metastasizing to mediastinal lymph nodes.
Structural Abnormalities	Aortic Aneurysm: Dilation of the aortic wall due to degeneration or hypertension, potentially compressing nearby structures. Oesophageal Diseases: Such as oesophageal cancer, diverticula, or perforation.
Immune and Inflammatory Causes	Sarcoidosis: An autoimmune disease characterized by mediastinal lymph node enlargement. Rheumatic Diseases: Such as rheumatoid arthritis may cause pleural or mediastinal inflammation.
Other Risk Factors	Ageing: Thymic tumours are more common in middle-aged and elderly individuals. Smoking and Long-Term Exposure to Carcinogens: Increases the risk of malignant tumours.

Diagnosis

Comprehensive diagnostic evaluations are necessary to identify the underlying cause and determine the extent of mediastinal diseases.

Clinical Examination	Detailed History: Inquiry about symptoms, disease progression, medical history, and family history. Physical Examination Focused assessment of the chest and lymph nodes to identify abnormalities.
Imaging Studies	Chest X-ray: Initial evaluation for abnormal shadows or structural changes in the mediastinal region. Computed Tomography (CT): High-resolution cross-sectional imaging to visualize structures and lesions in detail. Magnetic Resonance Imaging (MRI): Provides more explicit images of soft tissue abnormalities, such as neurogenic tumours. Positron Emission Tomography (PET-CT): Assesses the metabolic activity of tumours and aids in differentiating benign from malignant lesions.
Endoscopic Examinations	Bronchoscopy: Allows visualization of structures in the mediastinum through the airway and enables biopsy. Mediastinoscopy: Direct visualization of the mediastinum with the ability to collect tissue samples for pathological analysis.
Ultrasound-Guided Procedures	Endobronchial Ultrasound (EBUS): EBUS combines bronchoscopy with real-time ultrasound imaging for minimally invasive evaluation. Ultrasound probes penetrate the bronchial walls to examine subtle external airway structures. Physicians can obtain high-resolution images of mediastinal structures and perform biopsies for further analysis. Advantages: Real-time visualization, minimal invasiveness, and high diagnostic accuracy.