ObjectiveTo explore factors influencing voice outcome in patients with unilateral vocal fold paresis and paralysis (UVFP). MethodsA total of 578 patients diagnosed with UVFP by laryngeal electromyography and follow-up were included, including 286 males and 292 females, with an average age of (43.18 +/- 14.65) years (13-80 years). According to follow-up analysis, the patients were divided into a vocal improvement group (VIG) and a vocal nonimprovement group (VNG), and the differences in etiology, nerve injury type (recurrent laryngeal nerve [RLN] alone or with superior laryngeal nerve [SLN] injury) and degree (incomplete or complete RLN injury) between the two groups were compared. ResultsThere were 232 patients in the VIG and 346 patients in the VNG. In the VIG, 121 patients (52.16%) had idiopathic vocal fold paresis or paralysis, with a significantly higher proportion than the VNG (41.62%, p = 0.013). Patients with tumor compression, radiotherapy, or congenital factors only presented in the VNG, and there was no significant difference in the proportion of patients with different injury sites between the two groups. There was no significant difference in proportions of RLN injury and RLN+SLN injury between the two groups (p = 0.98). In the VIG, 168 patients (72.41%) had complete RLN injury, which was lower than the VNG (79.77%, p = 0.04). The specific injury types in thyroarytenoid muscles (TA) showed no differences between the two groups. But in posterior cricoarytenoid muscles (PCA) of the VIG, the proportion of decreased recruitment pattern combined with synkinesis was significantly reduced (p < 0.01). ConclusionsIdiopathic UVFP has a greater possibility of vocal improvement, while least possibilities were seen in those with tumor compression, radiotherapy, and congenital factors. Complete RLN injury is not conducive to vocal improvement, of which the PCA injury is more evident than TA muscle and PCA synkinesis may be a greater risk factor.