Phase difference of vocally healthy subjects in high-speed digital imaging analyzed with laryngotopography.

Background: To elucidate the vibratory patterns of the vocal folds in normophonic subjects, we conducted a prospective study with laryngotopography, an analyzing technique for high-speed digital imaging to intuitively grasp spatial characteristics of vocal fold vibrations by pixel-wise discrete Fourier transform for brightness curve.

Materials And Methods: Vocally healthy volunteer subjects with neither vocal complaint nor history of laryngeal diseases were divided into young (aged 35 years and younger) and elderly groups (aged 65 years and older), and high-speed digital images of phonations at a conversational frequency were analyzed with laryngotopography: phase differences (PDs) in the anterior-posterior (longitudinal) direction and in the left-right (lateral) direction were assessed.

Results: Twenty-six young subjects (nine men and 17 women with a mean age of 27 years) and 20 elderly subjects (eight men and 12 women with a mean age of 73 years) were assigned to our study. In longitudinal PD, posterior-to-anterior opening type was significantly frequent in young women (all subjects: 43% and young women: 94%; P<0.001), whereas anterior-to-posterior opening type was significantly frequent in elderly men (all subjects: 39% and elderly men: 88%; P<0.001). There were no age- or gender-related differences in lateral PD (all subjects: 65%; P=0.880).

Discussions: Both longitudinal and lateral PDs were widely observed even in vocally healthy subjects. Furthermore, the age- and gender-specific characteristics were also classified. Laryngotopography serves as a powerful tool to quantitatively characterize the vibratory patterns of vocal folds in vocally healthy subjects.