The Impact of Etiology on Time to Vocal Fold Motion Recovery in Unilateral Vocal Fold Paralysis

Spontaneous recovery of vocal fold (VF) motion in unilateral vocal fold paralysis (UVFP) has been shown to follow a bimodal time distribution for peripheral, nonidiopathic etiologies, but recovery time dependencies on UVFP etiology are incompletely characterized. This study aimed to (1) determine recovery time differences between surgically induced, idiopathic, and intubation-related UVFP, and (2) investigate the impact of distance of injury from larynx on recovery time in surgically induced UVFP.

Retrospective study of 1425 UVFP patients over a 16-year period identified 736 patients with recovery of VF motion. The time to the first laryngoscopic sign of VF motion recovery in surgically induced, idiopathic, or intubation-related UVFP was fit to a bimodal or unimodal mathematical model. Time course of VF motion recovery was also compared using Kaplan-Meier estimates.

Surgically induced UVFP demonstrated a bimodal time-to-recovery distribution, consistent with a previously described two-phase model of recovery. Both idiopathic and intubation-related UVFP followed unimodal recovery patterns. Among surgically induced cases, Kaplan-Meier recovery curves for thyroid/parathyroid and cardiothoracic surgeries were nearly identical despite differing injury locations along the recurrent laryngeal nerve.

Differences in the time course of VF motion recovery in UVFP reflect the underlying etiologies. Among surgically induced UVFP, the recovery time did not correlate with the distance between the injury site and the larynx, challenging a long-held assumption. The findings support a model in which the severity of neural injury, not the location of injury, is the principal determinant of time to recovery.