A 52-year-old man with Graves' disease undergoes total thyroidectomy. Intraoperatively, the surgeon carefully identifies and preserves both recurrent laryngeal nerves. On postoperative day 2, the patient develops hoarseness and weak voice. What is the most common cause of this complication?

Explanation

## Postoperative Hoarseness After Thyroidectomy ### Most Common Cause **Key Point:** Unilateral recurrent laryngeal nerve (RLN) injury is the most common cause of postoperative hoarseness after thyroidectomy, occurring in 0.5–2% of cases. ### Recurrent Laryngeal Nerve Anatomy and Vulnerability | Nerve | Course | Vulnerable Points | Injury Rate | |-------|--------|-------------------|-------------| | **Recurrent Laryngeal Nerve (RLN)** | Ascends in tracheoesophageal groove; enters larynx below inferior pharyngeal constrictor | Inferior thyroid pole, ligament of Berry, tracheoesophageal groove | 0.5–2% (unilateral) | | **Superior Laryngeal Nerve (SLN)** | Descends lateral to thyroid; external branch innervates cricothyroid | Upper pole of thyroid | 0.3–1% | | **Vagus Nerve** | Descends in carotid sheath | Rare unless carotid injury | <0.1% | ### Clinical Features of Unilateral RLN Injury - **Voice:** Hoarse, breathy, weak (loss of vocal cord adduction) - **Cough:** Weak, ineffective (loss of glottic closure) - **Laryngoscopy:** Ipsilateral vocal cord in paramedian position (abduction loss) - **Swallowing:** Usually preserved (bilateral function remains) - **Aspiration:** Minimal risk with unilateral injury ### High-Yield Facts **High-Yield:** RLN injury is more common than SLN injury in thyroidectomy because the RLN has a longer, more tortuous course and passes through the operative field at the lower pole. Most RLN injuries are transient (neuropraxia) and resolve within 3–6 months; permanent injury occurs in <0.5%. **Mnemonic:** RLN injury = **"Breathy, Weak, Hoarse"** (loss of adduction); SLN injury = **"Vocal fatigue, Loss of pitch control"** (loss of cricothyroid function). ### Prevention and Management 1. **Intraoperative RLN monitoring (IONM):** Real-time EMG feedback; improves identification and reduces injury 2. **Careful dissection:** Identify RLN early in the tracheoesophageal groove 3. **Postoperative voice rest:** Avoid straining; speech therapy if persistent 4. **Follow-up:** Laryngoscopy at 6–8 weeks if hoarseness persists beyond 3 months **Clinical Pearl:** Bilateral RLN injury causes stridor and airway obstruction (emergency); unilateral injury causes hoarseness only. The patient's presentation (hoarseness without stridor) confirms unilateral injury.