Clinical Significance of Asymmetrical Vocal Cord Tension

Abstract

The effects of asymmetrical tension on the vibratory pattern of the vocal cords were studied in two kinds of experiments: 1) high speed motion picture photography of artificial voice production in excised canine and human larynges, and 2) computer synthesis of voice and vocal cord vibration via a theoretical model incorporating the physiological parameters required for phonation. In both approaches the asymmetrically tensed vocal cords consistently vibrated in three distinct modes which depend partly on the rest positions of the vocal cords; Type I. For rest positions at or near closure, the two cords vibrate at the same frequency with glottal closure every period, and with tense cord preceding the lax one in phase and with the line of contact moving toward the tenser cord during the closed phase. The voice produced is not hoarse; Type II. For wider rest positions glottal closure occurs irregularly, the vibrations become complex and less periodic, and the voice becomes hoarse; Type III. The glottis never closes and the vibrations become more periodic with reduced amplitude. Supplementary stroboscopic observations suggest a precedure for diagnosing tension asymmetry and the implications for surgical treatment for disorders of vocal pitch are discussed.

Asymmetric vibration in a two-layer vocal fold model with left-right stiffness asymmetry: Experiment and simulation

“…Studies that reported a leading phase of the stiff fold over the soft fold (e.g., Isshiki et al, 1977;Sercarz et al 1992;Steinecke and Herzel, 1995) were likely to fall in the regime of relatively small stiffness mismatch. As shown in this study, in this regime, both folds were actively excited, and either fold can exhibit a relatively larger vibration amplitude, which also explains the contradictory observations regarding the left-right vibration amplitude difference in those studies.…”

“…There have been many previous studies on vocal fold vibration in asymmetric conditions (e.g., Isshiki et al, 1977;Sercarz et al, 1992;Moore et al, 1987;Smith et al, 1992;Berke and Gerratt, 1993;Steinecke and Herzel, 1995;Xue et al, 2010). While many studies (e.g., Ishizaka and Isshiki, 1976;Isshiki et al, 1977;Sercarz et al, 1992;Steinecke and Herzel, 1995;Pickup and Thomson, 2009;Xue et al, 2010) reported that the motion of the normal fold preceded the paralyzed fold in phase, the opposite (i.e., the soft fold leads in phase) was also reported (e.g., Moore et al, 1987).…”

“…For example, Sercarz et al (1992) observed a larger amplitude in the normal fold as compared to the paralyzed fold, whereas Pickup and Thomson (2009) reported a slightly larger vibration amplitude in the softer fold in their physical model experiments. Isshiki et al (1977) showed that generally the tense (normal) fold vibrated with the same or sometimes greater amplitude than the lax (paralyzed) fold. However, Isshiki et al (1977) also reported that the tense fold vibrated with a greatly reduced amplitude in the case of extreme tension imbalance.…”

“…Isshiki et al (1977) showed that generally the tense (normal) fold vibrated with the same or sometimes greater amplitude than the lax (paralyzed) fold. However, Isshiki et al (1977) also reported that the tense fold vibrated with a greatly reduced amplitude in the case of extreme tension imbalance. Such greatly reduced vibration amplitude of the tense or normal fold was also reported in the in vivo canine experiment of Moore et al (1987) and physical model experiments (Zhang, 2010b).…”

“…While many studies (e.g., Ishizaka and Isshiki, 1976;Isshiki et al, 1977;Sercarz et al, 1992;Steinecke and Herzel, 1995;Pickup and Thomson, 2009;Xue et al, 2010) reported that the motion of the normal fold preceded the paralyzed fold in phase, the opposite (i.e., the soft fold leads in phase) was also reported (e.g., Moore et al, 1987). Inconsistence also exists in the literature regarding the relative difference in vibration amplitude.…”