What is the workup for unilateral vocal fold paralysis?

Workup for Unilateral Vocal Fold Paralysis

The definitive workup for unilateral vocal fold paralysis should begin with laryngoscopy to confirm the diagnosis, followed by imaging from the skull base to the thoracic inlet/arch of the aorta to identify the etiology, with consideration of laryngeal electromyography (LEMG) for prognostic information. 1

Initial Evaluation

Laryngoscopy

• Laryngoscopy is the primary diagnostic modality and must be performed before any imaging studies 1
• Allows for:
  • Confirmation of vocal fold paralysis versus mechanical fixation
  • Assessment of the position of the paralyzed vocal fold
  • Evaluation of compensatory mechanisms
  • Identification of other laryngeal pathologies

History and Focused Assessment

• Identify potential causes:
  • Recent surgical procedures (especially thyroid, cardiac, or thoracic)
  • History of intubation or neck trauma
  • Neurological symptoms
  • Voice use patterns and professional voice demands
  • Onset and progression of symptoms
• Document associated symptoms:
  • Dysphagia
  • Aspiration
  • Shortness of breath
  • Other cranial nerve deficits (suggesting high vagal lesion)

Imaging Studies

CT or MRI

• After laryngoscopy confirms vocal fold paralysis, imaging from skull base to thoracic inlet/arch of aorta is warranted 1
• This approach evaluates the entire course of the recurrent laryngeal nerve:
  • Left side: as it loops around the arch of the aorta
  • Right side: as it loops around the subclavian artery

Specific Imaging Recommendations

• For isolated recurrent laryngeal nerve paralysis: CT scan from skull base through upper mediastinum 2
• For high vagal signs/symptoms: MRI of the skull base (may need additional CT if MRI is negative) 2
• For skull base lesions: MRI of brain and brainstem with gadolinium enhancement 1
• For additional lower cranial nerve palsies: Focused evaluation of jugular foramen (CN IX, X, XI) 1
• For children: MRI is preferred due to radiation concerns with CT 1

Specialized Testing

Laryngeal Electromyography (LEMG)

• Useful for:
  • Differentiating between neurogenic and mechanical causes of immobility 1
  • Providing prognostic information about potential recovery 1
  • Identifying the presence of vocal fold paresis (partial paralysis) 1, 3
• Most valuable when performed between 21 days and 6 months post-onset 1
• LEMG findings that indicate poor prognosis:
  • Reduced motor unit recruitment
  • Decreased interference pattern
  • Presence of spontaneous activity (fibrillation potentials or positive sharp waves) 1

Additional Tests (Based on Clinical Findings)

• Esophagoscopy or esophagram if esophageal obstruction is suspected 2
• Neurological consultation if non-ipsilateral neurologic signs are present 2
• Voice acoustic analysis to document severity and monitor progress 4

Common Pitfalls and Caveats

1. Delayed Diagnosis: Failing to perform laryngoscopy early can delay diagnosis of potentially serious underlying conditions 1

2. Inadequate Imaging: Not imaging the entire course of the recurrent laryngeal nerve can miss the causative lesion 1

3. Misdiagnosis: Confusing arytenoid dislocation/fixation with true neurogenic paralysis (LEMG can help differentiate) 1

4. Premature Intervention: Making permanent surgical decisions before determining if spontaneous recovery will occur (LEMG can provide prognostic information) 1, 5

5. Overlooking Idiopathic Cases: Approximately one-third of cases may be idiopathic, requiring thorough evaluation to rule out other causes 6, 4

6. Radiation Exposure: Using CT in children when MRI would be more appropriate due to radiation concerns 1

7. Missing High Vagal Lesions: Not evaluating for additional cranial nerve deficits that would suggest a more proximal lesion 1, 2

By following this systematic approach to the workup of unilateral vocal fold paralysis, clinicians can identify the underlying cause and develop an appropriate management plan to optimize outcomes related to voice quality, swallowing function, and airway protection.