## Recurrent Laryngeal Nerve and Thyroid Surgery **Key Point:** The recurrent laryngeal nerve (RLN) is the most commonly injured nerve during thyroid surgery because it passes through the thyroid capsule and ligament of Berry as it ascends to innervate the larynx. ### Anatomical Course of RLN The recurrent laryngeal nerve has an asymmetrical course: - **Right side:** Loops around the subclavian artery - **Left side:** Loops around the aortic arch - Both ascend in the **tracheoesophageal groove** and pierce the thyroid capsule medially ### Why RLN is Vulnerable 1. Intimately related to the inferior thyroid artery 2. Passes through the thyroid capsule at the ligament of Berry 3. Variable anatomical course (may be non-recurrent in 0.3–1% of cases) 4. Injury results in vocal cord paralysis and hoarseness ### Comparison with Other Nerves | Nerve | Relationship to Thyroid | Injury Risk | |-------|-------------------------|-------------| | **RLN** | Passes through capsule | **Very High** | | **SLN (external)** | Runs lateral to superior pole | Moderate | | **Vagus** | Lies in carotid sheath, lateral | Low | | **GPN** | Remote, pharyngeal plexus | Very Low | **High-Yield:** RLN injury is the most common iatrogenic nerve injury in head and neck surgery. Bilateral RLN injury causes airway obstruction and is a surgical emergency. **Clinical Pearl:** The ligament of Berry (suspensory ligament) is where the RLN most commonly enters the thyroid capsule—this is the critical point of dissection during thyroidectomy. 
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