Cepstral Peak Prominence: A Valuable Measure of Voice Outcome Severity in Patients With Unilateral Vocal Fold Paralysis

Objectives: This study investigated the relationship between the position of the paralyzed vocal fold and voice quality in patients with unilateral vocal fold paralysis (UVFP) and identified a reliable acoustic analysis tool to enhance the accuracy of voice quality assessments in this population.

Methods: A retrospective case-control study was conducted with 70 patients with UVFP diagnosed at Mackay Memorial Hospital. Acoustic features-jitter, shimmer, the harmonic-to-noise ratio (HNR), and the cepstral peak prominence smoothed (CPPs)-were analyzed using the Praat software. A speech-language pathologist performed an auditory-perceptual assessment by using a perceptual voice evaluation scale, and a senior laryngologist reviewed the paralyzed fold's position endoscopically. Spearman's linear regression analysis was used to examine correlations between perceptual and acoustic parameters and the position of the paralyzed vocal fold.

Results: The position of the paralyzed vocal fold exhibited weak correlations with acoustic and auditory-perceptual variables (r = 0.205-0.39). By contrast, moderate-to-strong correlations were discovered between auditory-perceptual variables and acoustic parameters (r = 0.378-0.803). Notably, the CPPs was more strongly associated with overall grade (severity: r = 0.673) and breathiness (r = -0.803) than with jitter, shimmer, and the HNR (r = 0.378-0.614).

Conclusions: The position of the paralyzed vocal fold alone is insufficient for predicting voice outcomes in patients with UVFP. The CPPs is a more valuable indicator of perceived dysphonia severity, particularly in cases with audible breathiness, making it superior to jitter, shimmer, and the HNR for perceptual voice assessments in patients with UVFP.