ENT: Bilateral Abductor Vocal Cord Paralysis
High-Yield Revision Notes for Board Review & PG Entrance Examinations
Complete (or bilateral abductor) paralysis of the larynx occurs when both vocal cords are paralyzed in the paramedian (adducted) position. This is a life-threatening emergency because the airway is severely compromised.
1. Pathophysiology (Semon’s Law)
- Semon’s Law: In progressive lesions of the recurrent laryngeal nerve (RLN), the abductor fibers (posterior cricoarytenoid muscle) are affected before the adductor fibers (lateral cricoarytenoid muscle).
- The Result: The cords fail to abduct (open) for inspiration, leading to inspiratory stridor, while voice quality remains relatively good (as adduction is preserved).
2. Clinical Presentation
- Airway Symptoms: Dyspnea on exertion and inspiratory stridor.
- Voice: Surprisingly good (near-normal phonation) because the cords are close to the midline.
- Cough: Strong and effective (because glottic closure is intact).
3. Common Etiologies
- Post-Surgical: Most common cause, specifically total thyroidectomy (due to bilateral RLN damage).
- Neoplastic: Malignancy of the thyroid, esophagus, or lung (pancoast tumor) affecting both nerves.
- Neurological: Brainstem strokes or severe neuritis.
4. Management & High-Yield Points
| Point | High-Yield Detail |
|---|---|
| Emergency Management | Emergency Tracheostomy is mandatory if the patient presents with severe respiratory distress. |
| Surgical Correction | Cord Lateralization (Arytenoidectomy): Procedures like Woodman’s operation or endoscopic laser arytenoidectomy to widen the glottic aperture. |
| Wagner-Grossman Theory | Explains that total RLN paralysis results in the cord remaining in the paramedian position (due to remaining tone of the cricothyroid muscle supplied by the Superior Laryngeal Nerve). |
| Diagnostic Pearl | If you see a paralyzed cord, always rule out a thyroid mass or occult malignancy along the entire course of the RLN (from the aortic arch to the larynx). |