Modifications of vestibular fold shape from respiration to phonation in unilateral vocal fold paralysis

The diversity of vestibular fold (VeF) behavior during phonation, as well as the lack of insight regarding both the anatomy and muscle fiber composition hinder our understanding of their role during phonation. The concave shape of the free margin of VeF appears to be standard, but little is known regarding the variability of this shape. We, therefore, sought to determine the laryngoscopic features related to changes in the free margin of the VeFs during phonation in patients with unilateral vocal fold paralysis. Laryngeal images from 39 patients with unilateral paralysis associated with recurrent laryngeal nerve damage were evaluated with regard to variations in length and shape of the VeFs (concave, straight, or convex) during both respiration and phonation. The VeFs on both the paralyzed and unaffected sides were analyzed during both phonation and respiration resulting in 156 total images. During phonation, all VeFs on the nonparalyzed side were straight or convex, whereas on the paralyzed side, only 20 of the 39 were straight or convex during phonation. During respiration, significant differences in the shape of the nonparalyzed side were observed. During phonation, a nonconcave appearance on the paralyzed side usually correlated with a similar appearance during respiration. VeF length decreased during phonation in 30 nonparalyzed VeFs in contrast to only 13 paralyzed folds. When subjects switched from respiration to phonation, the VeFs were typically nonconcave on the nonparalyzed side. In contrast, on the paralyzed side, nonconcave VeFs were consistent across both tasks. In patients with unilateral vocal fold paralysis, VeF conformation is likely determined from extralaryngeal than intrinsic muscle. These findings have important theoretical considerations for laryngeal treatment.