A 58-year-old man presents to the ENT clinic with progressive hoarseness and dysphagia for 3 weeks. He has a history of hypertension controlled on antihypertensive medications. On examination, he has a weak cry and stridor is absent. Flexible laryngoscopy reveals bilateral vocal cord paralysis in the paramedian position. CT chest with contrast shows a 4 cm mass in the superior mediastinum compressing the trachea. What is the most likely diagnosis underlying the vocal cord paralysis?

Explanation

## Clinical Presentation and Pathophysiology Bilateral vocal cord paralysis in the paramedian position with a mediastinal mass is a classic presentation of **recurrent laryngeal nerve (RLN) compression** by a mediastinal pathology. ### Anatomical Basis **Key Point:** The recurrent laryngeal nerve has a long intrathoracic course — the left RLN loops under the aortic arch, and the right RLN loops under the subclavian artery. Both nerves are vulnerable to compression by mediastinal masses. ### Why Mediastinal Lymphoma? **High-Yield:** Mediastinal lymphoma (particularly Hodgkin lymphoma and primary mediastinal B-cell lymphoma) is the most common **non-malignant mediastinal mass** causing bilateral RLN compression and paralysis. The superior mediastinal location and size (4 cm) are typical. ### Paramedian Position Significance **Clinical Pearl:** Bilateral paramedian vocal cord position indicates: - Both RLNs are affected (ruling out unilateral pathology) - The cords are not fully abducted (suggesting RLN paralysis rather than superior laryngeal nerve involvement) - This creates a narrow airway, explaining both hoarseness and dysphagia ### Differential Considerations | Finding | Mediastinal Lymphoma | Thyroid Carcinoma | Carotid Dissection | Idiopathic | |---------|---------------------|-------------------|-------------------|----------| | **Bilateral involvement** | Common (mediastinal mass) | Rare (usually unilateral) | Extremely rare | Possible but diagnosis of exclusion | | **Imaging finding** | Mediastinal mass on CT | Thyroid mass on CT/ultrasound | Arterial dissection on CTA | No structural lesion | | **Paramedian position** | Expected (RLN compression) | Expected (RLN involvement) | Unexpected | Expected | | **Age/demographics** | Any age, often young adults | Typically older | Trauma history common | Any age | **Mnemonic — Causes of Bilateral RLN Paralysis: SLIM** - **S** — Sarcoidosis, Superior mediastinal mass - **L** — Lymphoma, Laryngeal web - **I** — Idiopathic - **M** — Mediastinal pathology, Malignancy ### Why the Mediastinal Mass is Lymphoma 1. **Size and location**: 4 cm superior mediastinal mass — classic for lymphoma 2. **Bilateral RLN involvement**: Both nerves compressed symmetrically by a central mass 3. **No thyroid involvement**: CT shows mass in mediastinum, not thyroid 4. **Systemic disease pattern**: Lymphoma commonly presents with mediastinal involvement **Key Point:** Thyroid carcinoma typically causes **unilateral** RLN paralysis via direct invasion or lateral neck node metastases, not bilateral compression from a mediastinal mass. ### Clinical Management Implications - Urgent ENT and oncology review - Biopsy of mediastinal mass (core needle or mediastinoscopy) - Staging CT/PET-CT for lymphoma - Airway assessment — bilateral paramedian cords may require tracheostomy if stridor develops [cite:Stell & Maran's Textbook of Head and Neck Surgery & Oncology Ch 26]