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AN38.1-3 | Larynx — Summary & Reflection
REFLECT
A 60-year-old woman with a history of rheumatic heart disease and mitral stenosis (moderate, untreated) presents with progressive hoarseness of 3 months. She has no neck swelling and a normal thyroid gland on examination. Indirect laryngoscopy reveals left vocal cord paralysis (cord in paramedian position). CXR shows an enlarged cardiac silhouette.
What is the diagnosis? What is the anatomical explanation? What is the eponymous name for this syndrome? Which specific structure is compressing which nerve? What is the management? If this patient also needed a thyroid operation for an incidental nodule, why would the left side be anatomically "safer" from an RLN perspective than a similar operation in a patient with a normal mediastinum?
KEY TAKEAWAYS
Larynx — Key Points:
- Cartilages: thyroid (largest, Adam's apple), cricoid (only complete ring), epiglottis (elastic, protects airway); paired: arytenoids (vocal + muscular processes), corniculate, cuneiform
- Compartments: vestibule (supraglottis) → ventricle → subglottis; glottis = vocal cords + rima glottidis
- Narrowest point: rima glottidis (adult); subglottis/cricoid ring (child) — explains croup stridor
- Intrinsic muscles: all = RLN EXCEPT cricothyroid (external SLN); PCA = ONLY abductor; LCA + arytenoids = adductors; cricothyroid = tenses/lengthens cord (pitch)
- RLN course: right loops under subclavian; left loops under aortic arch (ligamentum arteriosum) — both ascend in tracheo-oesophageal groove → enter larynx posterior to cricothyroid joint
- Unilateral RLN injury: hoarseness (cord paramedian); bilateral: stridor + respiratory failure → emergency tracheostomy
- Non-recurrent RLN (right, 0.5–1%): direct transverse course; associated with aberrant right subclavian artery; surgical trap
- Lymphatics: glottis = almost none (T1 glottic = best prognosis); supraglottis = rich, bilateral (early N+)
- Croup: subglottic oedema encircled by inelastic cricoid → stridor; steeple sign on X-ray; treat with dexamethasone
- Emergency airway: cricothyrotomy = cricothyroid membrane (between thyroid and cricoid cartilages)