Objective:
Stimulability testing is frequently used in managing phonotraumatic vocal fold lesions (PVFLs) to identify strategies that may improve phonatory ease and quality. High-speed videoendoscopy (HSV) enables direct visualization of vocal fold kinematics, and cepstral peak prominence (CPP) is an objective acoustic correlate of voice quality and spectral periodicity. Though increases in CPP are traditionally interpreted as improvement, CPP may instead reflect movement toward the individual’s optimal physiological target. For some, therapeutic focus involves reducing pressed phonation and increasing airflow, which may decrease CPP despite perceptual improvement. For others, efficient resonance and balanced phonation could increase CPP. This study examined whether (1) average HSV parameters change after stimulability testing and (2) CPP direction reflects distinct physiologic patterns.

Methods:
Twenty-eight women with PVFLs were assessed before and after a standardized stimulability protocol. HSV was conducted on /i:/ in modal register using a transoral rigid scope. Exams were collected at 4000 frames per second. HSV parameters included closing quotient (ClQ), maximum area declination rate (MADR), speed index (SI), and stiffness index (STI). CPP was extracted from connected speech. Paired t-tests examined pre- to post-changes in HSV variables and CPP. Exploratory analyses tested whether CPP direction of change (increase vs. decrease) moderated physiologic response (time × group).

Results:
As a single cohort, no significant pre/post changes were observed in HSV parameters or CPP. However, CPP direction revealed divergent physiologic patterns. Time × CPP-direction interactions were significant for ClQ (p = .002) and STI (p = .035) and approached significance with medium effect sizes for SI (p = .087) and MADR (p = .083; both η² = .11). Reduced CPP was associated with slower, less forceful closure.

Conclusions:
Reduction of CPP after stimulability showed kinematic changes consistent with reduced hyperfunction and greater airflow release. Increased CPP showed vibratory patterns associated with faster vocal fold closure, consistent with enhanced resonance. While both groups reported improvement, they achieved this through different physiological pathways. Lack of overall group change may conceal meaningful subgroups defined by therapeutic target. Findings provide preliminary support of CPP as an accessible indicator of individualized physiological shifts following stimulability testing.