Impact of Vocal Fold Opening Position on Bowing Measures in Age-Related Vocal Atrophy: Clinical Implications and Future Directions

Highlight

• Vocal fold bowing in age-related vocal atrophy (ARVA) varies significantly with vocal fold positioning during voice tasks.
• Bowing Index (BI) is greater during vocal fold abduction compared to adduction, with highest bowing observed at semi-abducted positions.
• BI correlates with clinical severity of ARVA, supporting its potential as an objective measure for disease monitoring.
• Standardization of BI measurement protocols is necessary to improve clinical assessment and guide therapeutic interventions.

Study Background

Age-related vocal atrophy (ARVA), also termed presbyphonia, is a prevalent condition characterized by thinning and bowing of the vocal folds resulting from age-associated degeneration of laryngeal muscles and connective tissue. This condition impairs phonatory function, leading to voice weakness, breathiness, and reduced vocal endurance, significantly impacting patients’ quality of life. Despite its clinical relevance, quantitative assessment of vocal fold bowing—a hallmark feature of ARVA—remains challenging, limiting objective diagnosis and treatment monitoring.

The Bowing Index (BI) is a morphometric tool utilized to quantify vocal fold bowing on laryngoscopic imaging, yet there is limited understanding of how dynamic vocal fold positioning during different tasks affects BI measurements. Specifically, the impact of vocal fold abduction (opening) versus adduction (closing) and intermediate positions on BI has not been fully elucidated. Clarifying these relationships is critical for establishing reliable and reproducible BI assessment methods in clinical and research settings.

Study Design

The study was conducted on a cohort of 22 patients diagnosed with ARVA. Using flexible video laryngostroboscopy, vocal fold motion was recorded during an alternating voice-sniff task designed to elicit transitions from complete adduction to full abduction. Non-phonatory frames—images captured during transitions without voicing—were selected for analysis.

The Bowing Index was measured at multiple points across these frames to evaluate the degree of vocal fold bowing. Two experienced clinical raters independently assessed each subject’s clinical severity of vocal atrophy (categorizing as mild, moderate, or severe) based on standard clinical criteria. These ratings were then compared with the corresponding BI values for validation.

Key Findings

Analysis revealed a statistically significant difference in BI values depending on the vocal fold task and opening angle:

• The mean BI during vocal fold abduction was 8.15 ± 3.29, compared to 6.34 ± 2.21 during adduction, representing a mean difference of 1.81 (95% CI: 1.25–2.38; p < 0.0001). This indicates that bowing appears more pronounced when folds are abducted (open) than adducted (closed).
• Within the abduction range, the greatest bowing was observed when the vocal folds were between 40% and 60% of maximal abduction, with a mean BI significantly higher than positions close to full abduction (80%-100%): mean difference 2.61 (95% CI: 1.26–3.96; p < 0.0001). This highlights a distinctive non-linear relationship between glottic angle and bowing severity.
• Clinical severity ratings corresponded with BI values: mild cases averaged a BI of 7.30 ± 1.85, moderate cases 8.90 ± 2.52, and the single severe case exhibited a markedly higher BI of 14.62. This confirms BI’s potential utility in reflecting disease severity objectively.

These findings underscore that the degree of vocal fold bowing in ARVA is not a static feature but varies dynamically with glottic posture during voice tasks.

Expert Commentary

The study by Miller et al. provides important insights into the biomechanical characteristics of vocal fold bowing in ARVA. It elucidates how measurement of bowing is task-dependent, a factor hitherto insufficiently appreciated in clinical practice. This variability likely accounts for inconsistencies in prior BI assessments and may contribute to challenges in correlating bowing extent with clinical symptoms.

Understanding the dynamic nature of vocal fold configuration is crucial, as ARVA’s pathophysiology involves structural and functional changes at both muscular and connective tissue levels. Bowing may be exaggerated during partial vocal fold opening due to altered tension and glottic geometry in degenerative states.

However, the study’s sample size is moderate, and the single severe case limits robust severity stratification. Further studies with larger cohorts and inclusion of phonatory frames could enhance generalizability. Additionally, standardizing the task and frame selection for BI measurement is essential to enable cross-study comparisons and clinical adoption.

Clinicians should consider these dynamic factors when evaluating patients with presbyphonia and employing BI as a diagnostic or monitoring tool. The findings also lay groundwork for refining voice therapy and surgical interventions targeting the biomechanical deficits inherent to ARVA.

Conclusion

This study decisively demonstrates that vocal fold bowing in age-related vocal atrophy is significantly influenced by the degree of vocal fold opening and the nature of the task performed during endoscopic evaluation. The Bowing Index is highest during abduction tasks, especially at semi-abducted glottic positions, and correlates with clinical severity measures.

These observations warrant consideration in clinical assessments and underscore the need for standardized BI measurement protocols to improve diagnostic consistency and therapeutic monitoring in ARVA. Future research should focus on expanding cohort diversity, integrating phonatory conditions, and exploring longitudinal changes to optimize care for patients suffering from age-related voice impairment.

Funding and Clinical Trials

The publication did not disclose specific funding sources or clinical trial registrations. Ongoing support and larger-scale studies would be instrumental to validate and extend these pivotal findings.

References

• Miller CS, Kim BS, Al-Ghezi M, Jaleel ZA, Zughni LA, Bhatt NK. Vocal Fold Opening Position Impacts Bowing Measures in Age-Related Vocal Atrophy. The Laryngoscope. 2026 Jul 4. PMID: 42400442.
• Hirano M. Morphological structure of the vocal cord as a vibrator and its variations. Folia Phoniatr Logop. 1974;26(2):89-94.
• Goudsmit E, Baken RJ, Diehl JR. The use of the glottic angle in the quantitative assessment of vocal fold bowing. J Voice. 1996;10(3):277-83.