Qualitative Analysis of Vocal Fold Vibration in Normal Adults with a High-Speed Video System

Background & Objectives: Reliable and accurate imaging analysis is critical for diagnosis and evaluation of abnormal vocal fold vibration. Unlike stroboscopy, high-speed digital imaging (HSDI) and videokymography (VKG) are frequency-independent visualization techniques that provide detailed information on biomechanical properties and vocal physiology by capturing increased laryngeal images within a limited time. Although the current gold standard for the clinical visualization technique of vocal fold vibration is stroboscopy, the technique may fail to yield an accurate analysis of vibratory irregularities. The present study investigated the vocal fold vibration pattern in normal Korean adults with a recently developed HSDI and VKG simultaneously. Methods: A total of 38 Korean healthy adults (females 23, males 15) without known voice problems were examined with HSDI to analyze the vocal vibratory characteristics. Glottal closure, mucosal wave, vibratory amplitude, vibratory symmetry, periodicity of vibration, and phase closure of the glottal cycle were judged during /i/ vowel phonation at comfortable pitch and loudness by 2 experienced raters to determine the normal vocal vibratory features, and compare the vibratory patterns for gender differences qualitatively. Additionally, VKG was used to determine in more detail the propagation of mucosal waves, right-left vocal fold symmetry, aperiodicity, and closed phase in the glottal cycle. Results: The most common glottal configuration was a posterior glottal gap in 54% of the study population. Posterior glottal gap was identified predominantly in females, whereas complete glottal closure was observed mostly in males. Mucosal wave, vibratory amplitude, vibratory symmetry, and periodicity of vibratory patterns were not statistically significantly different between males and females (p > 0.05), whereas adult males predominantly showed closed phase in the glottal cycle compared to females (p < 0.05). The ratings of mucosal wave and vibratory amplitude were observed to be around normal mark. However, asymmetry of vibration between right and left vocal folds was identified in 13% of the study population with the HSDI and VKG. Discussion & Conclusion: Although normal voice demonstrated predominantly posterior glottal gap or complete glottal closure configuration, various glottal configurations including anterior glottal gap and hourglass were identified. In addition, asymmetry and aperiodicity of vocal vibration were also observed in normal adults suggesting that asymmetric and aperiodic vibration should not be considered as abnormal vibratory patterns.