声帯振動の解析

Abstract

The mucosal upheaval (MU) where the mucosal wave starts and propagates upward appears on the lower surface of the vocal fold during vibration. We investigated the location of the MU in response to variations in vocal fold tension and to contraction of the thyroarytenoid muscle (TA). Fresh excised larynxes (seven canine and four human) were used in the experiment. The lower surface of the vocal fold was tattooed with india ink as a reference point. Vocal fold vibration was observed either by high-speed filming or by videostroboscopy. Vocal fold tension was increased by cricothyroid approximation and TA contraction was obtained by its direct electrical stimulation. When vocal fold tension increased, the MU appeared medially or upward compared to its original position. With TA contraction, the lower surface of the vocal fold bulged medially and thus horizontal amplitude of the vibration became smaller. When TA contracted, the MU appeared less prominent and was located more downward compared to its position without TA contraction. These were basically common findings to both canine and human excised larynxes. Moreover, vocal fold vibration was stroboscopically observed through a tracheostoma in twelve patients. The MU occurred on the lower surface of the vocal fold as seen in the excised larynx and the mucosal wave was elicited upward from the MU.