A 58-year-old man presents with progressive hoarseness and dysphagia for 3 weeks. He has a 20-pack-year smoking history and works as a factory supervisor. On examination, he has stridor at rest and bilateral vocal cord immobility on laryngoscopy. CT chest reveals a 4 cm mass at the carina with mediastinal involvement. What is the most likely diagnosis underlying his vocal cord paralysis?

Explanation

## Clinical Presentation Analysis **Key Point:** Bilateral vocal cord paralysis (BVCP) in a smoker with mediastinal mass is lung cancer until proven otherwise. The carina involvement and mediastinal extension indicate advanced disease compressing or invading both recurrent laryngeal nerves. ## Pathophysiology of RLN Injury The recurrent laryngeal nerves have a long course through the mediastinum: - Left RLN loops under the aortic arch - Right RLN loops under the subclavian artery - Both nerves ascend alongside the trachea and esophagus Mediastinal masses (especially at the carina) can compress or invade both nerves simultaneously, causing bilateral paralysis. ## Differential Diagnosis of Bilateral VCP | Etiology | Frequency | Key Features | |----------|-----------|-------------| | Malignancy (lung, esophageal, thymic) | 40–50% | Mediastinal mass on imaging, progressive course | | Thyroid surgery | 20–25% | Bilateral surgical history, acute onset | | Idiopathic | 10–15% | Exclusion diagnosis, no identifiable cause | | Sarcoidosis | 5–10% | Systemic symptoms, hilar LAD, elevated ACE | | Trauma/intubation | 5% | Clear history of instrumentation | **High-Yield:** In a patient with smoking history, mediastinal mass, and bilateral RLN signs → lung cancer is the leading diagnosis. Carina involvement is particularly ominous for malignant invasion. ## Clinical Pearl Bilateral vocal cord paralysis presents with **stridor** (not just hoarseness) because both cords are in paramedian position, obstructing the airway. Unilateral paralysis causes only hoarseness. The presence of stridor at rest indicates airway compromise and potential need for tracheostomy. ## Why This Patient Has Bilateral Paralysis The 4 cm mass at the carina with mediastinal involvement is positioned to compress both recurrent laryngeal nerves as they ascend from the thorax. This is a classic presentation of advanced lung cancer causing malignant bilateral RLN palsy.