Vocal Fold Paralysis

Basics & Anatomy - Vocal Cord Voyage

• Vocal folds: True cords for voice. Layers: mucosa, Reinke's space, ligament, muscle.
• Vagus Nerve (CN X) supplies larynx.
  • Superior Laryngeal N. (SLN): Internal branch (sensory above cords), External branch (motor to cricothyroid - affects pitch).
  • Recurrent Laryngeal N. (RLN): Motor to all other intrinsic laryngeal muscles (abductors & adductors); sensory below cords. Left RLN longer (loops under aortic arch). 📌 SLN Sings (pitch), RLN Roars (voice).

⭐ The cricothyroid muscle, supplied by the external branch of the SLN, is the only laryngeal muscle that tenses the vocal cords, thus primarily responsible for pitch elevation.

Etiology - Silent Saboteurs

• Neoplastic: Lung (Pancoast), thyroid, esophageal, skull base tumors.
• Iatrogenic: Most common overall. Thyroid/cardiac surgery (RLN injury), intubation, neck dissection.
• Idiopathic: Diagnosis of exclusion. Viral/inflammatory suspected.
• Neurological:
  • Peripheral: Diabetic neuropathy, Guillain-Barré syndrome.
  • Central: Stroke (e.g., Wallenberg syndrome), MS, ALS.
• Trauma: Blunt or penetrating neck injuries.
• Other: Ortner's syndrome (cardiovocal due to left atrial enlargement).

⭐ Thyroid surgery is the most common iatrogenic cause of unilateral vocal fold paralysis due to Recurrent Laryngeal Nerve (RLN) injury.

Clinical Features - Signs of Silence

• Voice: Hoarseness, breathiness, diplophonia.
  • UVFP: Weak, airy.
  • BVFP: Variable; near normal (median) to aphonia (cadaveric).
• Aspiration: Coughing/choking on liquids.
• Airway:
  • UVFP: Usually normal.
  • BVFP: Stridor, dyspnea (esp. median/paramedian cords).
• Cord Positions & Impact:
  • Median: Good voice, poor airway.
  • Paramedian: Breathy, airway risk.
  • Cadaveric: Aphonia, aspiration, better airway.

⭐ Bilateral median position: Voice surprisingly good, severe airway compromise_

Diagnosis - Unmasking the Mute

• Key Investigations:
  • Laryngoscopy (Flexible/Rigid): Initial step. Confirms vocal fold (VF) immobility. Observe position (median, paramedian, cadaveric).
  • Videostroboscopy: Differentiates paralysis from fixation (e.g., cricoarytenoid joint). Assesses mucosal wave, amplitude, symmetry, periodicity.
  • Laryngeal Electromyography (L-EMG): Confirms neurogenic paralysis. Differentiates from mechanical fixation. Prognosticates recovery (detects reinnervation potentials).
  • Imaging (CT with contrast / MRI): Neck & chest (skull base to aorto-pulmonary window). Identifies underlying etiology (e.g., tumors, trauma, inflammation).

⭐ Laryngeal EMG is the gold standard to differentiate vocal fold paralysis from cricoarytenoid joint fixation and to assess for signs of reinnervation.

Management - Restoring the Voice

• Voice Therapy: Initial management. Focus on vocal hygiene, compensatory strategies, reducing phonatory effort.
• Injection Laryngoplasty: Temporary medialization for small-moderate glottic gaps.
  • Materials: Hyaluronic acid, CaHA, autologous fat. Duration: 3-12 months.
• Thyroplasty Type I (Medialization Laryngoplasty): Gold standard for permanent UVFP.
  • Isshiki Type I: Implant (Silastic, Gore-Tex) via thyroid cartilage window pushes fold medially.
• Reinnervation: For younger patients, good neuromuscular integrity. E.g., Ansa cervicalis-RLN anastomosis.
• Arytenoid Procedures: Arytenoid adduction, often combined with Type I thyroplasty for posterior gaps.
• Airway (Bilateral VFP): If dyspnea, consider tracheostomy, cordotomy, or arytenoidectomy.

⭐ Thyroplasty Type I (Isshiki) is the most common surgical procedure for achieving permanent voice improvement in unilateral vocal fold paralysis.

Awaiting image generation for "Illustration of Thyroplasty Type I procedure steps"...

High‑Yield Points - ⚡ Biggest Takeaways

• Recurrent Laryngeal Nerve (RLN) injury is the most common cause; left RLN is more vulnerable (e.g., thoracic lesions).
• Unilateral paralysis presents with hoarseness, breathy voice, and risk of aspiration.
• Bilateral abductor paralysis is an airway emergency causing inspiratory stridor.
• Semon's Law: Posterior cricoarytenoid (abductor) muscle fibers are more susceptible to injury.
• Paramedian position is the most common vocal fold position in unilateral RLN palsy.
• Thyroplasty Type I (medialization) is a key surgical treatment for symptomatic unilateral paralysis.