Abnormal adductor movement of the vocal cords in spasmodic dysphonia

Abstract

Adductor movement of the vocal cords in initial /ke/ phonation was recorded using a laryngeal fiberscope, CCD camera, and videocassette recorder. Three patients with adductor spasmodic dysphonia (SD), a 53 year old male and 48 and 52 year old females, and 7 normal volunteers participated in this study. During the examination, the subject sat on a chair holding a microphone about 20 cm away from his or her lips. A laryngeal fiberscope was inserted through either side of the nostril. The tip of the fiberscope was positioned just caudal to the tip of the epiglottis to get a complete view of both sides of the vocal cords. The examiner told the subject to make the speech sound /ke/ repeatedly, and to insert a sufficient inspiratory period between each phonation. The vocal cord images were recorded at 30 frames per second and printed successively from several frames ahead of the beginning of adductor movement to the frame of initial adjustment of the membranous part of the vocal cords following a time code indicator. The tips of both sides of the vocal processes and anterior commissure were marked, then, scanned and transported to a personal computer. An imaginary line connecting the vocal process and anterior commissure was drawn on the screen of the computer, which was done on both sides of the vocal cords. Then, an angle made by the two lines was measured in degrees and stored. The time and speed of adductor movement varied among subjects. Normal subjects, however, never failed to finish making the plosive sound in /ke/ before initial vocal cord adjustment. In contrast, in the SD patients, voiceless tight vocal adjustment occurred just before subsequent glottal opening to make a plosive sound. The degree of this abnormal closure seemed to be related to the severity of phonatory symptoms in these three patients. The conclusion was that the abnormal pattern of vocal cord movement required to make the /ke/ sound was present in the three SD patients, suggesting motor control dysfunction of the speech center. © 1993, The Oto-Rhino-Laryngological Society of Japan, Inc. All rights reserved.