What is the most likely cause of hoarseness after thyroid surgery?

Recurrent Laryngeal Nerve Injury is the Most Likely Cause of Hoarseness After Thyroid Surgery

Recurrent laryngeal nerve (RLN) injury is the most common cause of hoarseness following thyroid surgery, accounting for approximately 90% of cases with confirmed glottic paralysis. 1

Causes of Post-Thyroidectomy Hoarseness

Neural Causes (Most Common)

1. Recurrent Laryngeal Nerve (RLN) Injury

   • Occurs in approximately 3-8% of thyroid surgeries 1
   • Results in immobile and laterally displaced vocal fold
   • Causes inadequate closure of vocal folds during phonation
   • Leads to loss of vocal fold bulk, tone, and bowing
   • Presents as breathy voice, vocal fatigue, and hoarseness 1
   • Mechanisms of injury include:
     • Traction/stretching of the nerve during thyroid manipulation
     • Clamping or compression during surgery
     • Heat injury from electrocautery
     • Rarely, transection of the nerve 1

2. External Branch of Superior Laryngeal Nerve (EBSLN) Injury

   • Less common but still significant
   • Results in vocal fatigue, decreased pitch range, and inability to project voice
   • Physical findings include posterior laryngeal rotation and inferior displacement of affected vocal fold 1

Non-Neural Causes

1. Direct Cricothyroid Muscle Injury

   • Transient myositis or direct trauma
   • Similar symptoms to EBSLN injury 1

2. Regional Soft Tissue Injury

   • Laryngotracheal scarring with fixation
   • Strap muscle denervation or trauma
   • Local hematoma and/or edema
   • Results in voice fatigue, decreased vocal range, and lower pitch 1

3. Intubation-Related Injuries

   • Vocal fold trauma (edema, hematoma, laceration)
   • Granuloma formation
   • Arytenoid dislocation
   • General incidence: 6-13% 1, 2

4. Unrelated Intercurrent Upper Respiratory Tract Infection

   • Typically viral-related laryngitis unrelated to surgery 1

Clinical Presentation and Diagnosis

Patients with post-thyroidectomy hoarseness typically present with:

• Breathy voice
• Vocal fatigue
• Decreased pitch range
• Difficulty projecting voice
• Occasionally dyspnea or mild dysphagia 1

Proper diagnosis requires:

• Laryngoscopic examination to assess vocal fold mobility
• Stroboscopic evaluation for detailed vocal fold movement analysis
• Electromyography in selected cases to confirm neural injury 1, 3

Management Approach

1. Early Referral to Otolaryngology

   • Should be done promptly when hoarseness persists beyond the immediate postoperative period
   • Early evaluation ensures greater likelihood of improving voice outcomes 1

2. Treatment Options Based on Cause

   • For RLN injury:
     • Voice therapy for mild cases or temporary injuries
     • Surgical intervention for permanent injuries (injection laryngoplasty, laryngeal framework surgery, or reinnervation procedures) 1
   • For non-neural causes:
     • Targeted therapy based on specific etiology
     • Anti-inflammatory medications for edema or inflammation
     • Voice therapy for compensation techniques 1

Prognosis

• Transient RLN injuries typically recover within 4-6 weeks
• The majority of patients with post-thyroidectomy hoarseness show improvement in the long term 4
• Even with permanent vocal cord palsy, compensatory mechanisms often lead to acceptable voice quality over time 4
• Only a small percentage of patients experience persistent severe hoarseness 4

Important Considerations

• Preoperative and postoperative laryngoscopic examination is recommended to document vocal fold function
• Early intervention improves long-term voice outcomes
• Voice therapy should be initiated promptly for patients with persistent hoarseness
• Surgical interventions for permanent vocal fold paralysis are highly effective when performed by experienced surgeons 1

Remember that while the endocrine surgeon's technique is crucial, other factors including intubation-related trauma can contribute to post-thyroidectomy hoarseness 2.