Disease Characteristics and Electromyographic Findings of Nonsurgery-Related Unilateral Vocal Fold Paralysis

Objective: The detailed characteristics and prognosis of nonsurgery-related unilateral vocal fold paralysis (NSUVFP) are currently unclear. This study evaluated the extent of laryngeal nerve lesions and the individual characteristics for patients with NSUVFP. Study Design: Retrospective, case series. Methods: Patients with unilateral vocal fold paralysis (UVFP) were evaluated using videolaryngostroboscopy and quantitative laryngeal electromyography. The side of nerve lesions, involvement of the external branch of the superior laryngeal nerve (eSLN), and complete vocal fold motion recovery were evaluated after >= 6 month follow-up. Results: A total of 207 UVFP patients were recruited, including 153 surgery-related UVFP and 54 NSUVFP patients. Thirty-four (63%) and 20 (37%) NSUVFP patients were further assigned to idiopathic and nonsurgery-related-nonidiopathic (NSNI) groups, respectively. In the idiopathic group, eSLN lesions occurred in all six (100%) patients with right-side paralysis, but in only six of 28 (21%) patients with left-side paralysis (P < 0.001). The turn frequency of the paralyzed thyroarytenoidlateral cricoarytenoid muscle complex is lower in the NSNI group (333.1 +/- 192.1) compared with the idiopathic group (490.2 +/- 255.1) (P = 0.02). The probability of complete vocal fold motion recovery did not differ among groups (P > 0.05). Conclusion: Idiopathic and NSNI UVFP have different clinical presentations defined by laryngeal electromyography. NSNI UVFP had more severe denervation changes compared with idiopathic UVFP. These results may support two pathogenic mechanisms for idiopathic UVFP: 1) neuropathy specifically involving left recurrent laryngeal nerve (RLN), and 2) neuropathy affecting nerves proximal to the RLN.