What is the prognostic significance of Laryngeal Electromyography (EMG) findings, including fibrillation and polyphasic patterns, in predicting outcomes?

From the Guidelines

Laryngeal electromyography (EMG) should be performed at 3-6 months after vocal fold paralysis to help predict recovery potential. This timing is optimal because it allows for initial nerve regeneration processes to begin while still being early enough to guide intervention decisions, as suggested by the study published in Otolaryngology--head and neck surgery 1. During the procedure, the presence of fibrillation potentials and positive sharp waves, which indicate ongoing denervation, suggests poor prognosis for spontaneous recovery. Conversely, polyphasic potentials and a "picket fence" pattern of motor unit recruitment during voluntary activity are positive prognostic indicators, suggesting successful reinnervation is occurring.

Key Findings

• The study found that serial LEMG examinations in the same patient over time may be helpful in predicting persistent vocal fold paralysis, with a sensitivity of 91% and specificity of 44% 1.
• Judgment of motor unit recruitment on LEMG was most useful for prediction, but was unblinded, highlighting the need for further prospective blinded studies to confirm these findings.
• The physiological basis for these findings relates to nerve degeneration and regeneration processes - fibrillations represent spontaneous firing of denervated muscle fibers, while polyphasic potentials represent newly formed neuromuscular junctions during reinnervation.

Clinical Implications

• Laryngeal EMG findings help clinicians determine whether to continue observation or proceed with more definitive interventions like medialization procedures.
• The test involves inserting small needle electrodes into laryngeal muscles to record electrical activity both at rest and during phonation, providing objective information that complements other clinical assessments in managing vocal fold paralysis.
• The importance of the LEMG prognosis on surgical decision is dependent on knowing how LEMG‑driven surgical outcomes are superior to other management approaches for vocal fold paralysis, as noted in the study 1.

From the Research

Laryngeal EMG Findings and Outcomes

• Fibrillation and peak waves are associated with failure, indicating a poor prognosis for recovery 2
• Polyphasic and picket fence patterns are associated with positive outcomes, suggesting a better prognosis for recovery 2

Timing of Laryngeal EMG

• Laryngeal EMG should be performed 3-6 months after the onset of vocal fold paralysis to predict recovery 2
• If prognostic information is required in a patient with vocal fold paralysis that is more than 4 weeks and less than 6 months in duration, then LEMG should be performed 2

Clinical Utility of Laryngeal EMG

• Laryngeal EMG is a useful diagnostic tool that contributes significantly to the evaluation and management of motion disorders in the larynx of dysphonic patients 3
• LEMG can help differentiate abnormal function of the vocal folds from nonorganic disorders and confirm the diagnosis of vocal fold paralysis (VFP) 4
• Laryngeal EMG can guide therapeutic injections into the laryngeal muscles and assess the prognosis for patients with VFP 4

Interpretation of Laryngeal EMG Results

• Abnormalities detected by LEMG are always interpreted within the context of the clinical picture 5
• LEMG should be considered an extension of the physical examination, not an isolated laboratory procedure 5