Which statement is true about subcutaneous and mediastinal emphysema?

Which statement is true about subcutaneous and mediastinal emphysema?

• A. Mediastinal emphysema is a prerequisite for subcutaneous emphysema
• B. Subcutaneous emphysema occurs when gas migrates into the neck from the mediastinum
• C. Subcutaneous emphysema occurs independently of mediastinal emphysema
• D. Subcutaneous emphysema cannot involve the neck

Answer: (B)