In bilateral vocal cord paralysis, which position do the vocal cords typically assume, and what is the primary clinical consequence?

Explanation

## Bilateral Vocal Cord Paralysis: Position and Clinical Features **Key Point:** In bilateral vocal cord paralysis, both cords assume a paramedian position, which creates a critically narrowed airway and causes stridor rather than voice changes. ### Pathophysiology of Bilateral RLN Paralysis When both recurrent laryngeal nerves are damaged: 1. Both vocal cords lose all intrinsic muscle innervation (except cricothyroid) 2. Both cords settle into the **paramedian position** bilaterally 3. The narrowed glottic space (bilateral paramedian cords) causes airway obstruction 4. This results in **inspiratory stridor**, the hallmark clinical sign ### Why Stridor, Not Hoarseness? | Feature | Bilateral Paramedian | Unilateral Paramedian | |---------|---------------------|----------------------| | Airway patency | Severely compromised | Adequate | | Primary symptom | **Stridor** (airway obstruction) | **Hoarseness** (voice quality) | | Voice quality | May be relatively preserved | Breathy, weak | | Breathing difficulty | Present (may be severe) | Absent | | Stridor | Yes, inspiratory | No | **High-Yield:** The key distinction is that bilateral paramedian cords cause an **airway problem** (stridor), while unilateral paramedian cords cause a **voice problem** (hoarseness). This is frequently tested in NEET PG. ### Clinical Presentation of Bilateral Vocal Cord Paralysis **Mnemonic: BIPOLAR** (Bilateral Paralysis Obstructs Laryngeal Airways Requiring emergency) - **B**reathing difficulty (stridor) - **I**nspiratory stridor (worse on inspiration) - **P**aramedian position of cords - **O**bstructed airway - **L**aryngoscopy shows narrow glottis - **A**irway management needed (tracheostomy may be required) - **R**are hoarseness (voice is secondary concern) ### Common Causes of Bilateral Vocal Cord Paralysis 1. **Thyroid surgery** (bilateral thyroidectomy or bilateral nerve injury) 2. **Intubation trauma** (prolonged mechanical ventilation) 3. **Idiopathic** (autoimmune, viral) 4. **Neurological**: Guillain-Barré syndrome, myasthenia gravis 5. **Malignancy**: Bilateral lung cancer, mediastinal masses 6. **Trauma**: Bilateral neck trauma **Clinical Pearl:** Bilateral vocal cord paralysis is a medical emergency. Patients may present with acute stridor and respiratory distress. Unlike unilateral paralysis (which is often asymptomatic), bilateral paralysis requires urgent intervention, potentially including tracheostomy or laser-assisted arytenoidectomy to widen the airway. ### Why Other Positions Are Wrong - **Lateral position**: Would occur if abductors were preserved; creates an open airway (no stridor) - **Median position**: Would occur if adductors were preserved; causes aphonia but not stridor - **Anterior position**: Not a recognized position in vocal cord paralysis [cite:Dhingra 8e Ch 12]