Sustained phonation is a part of the vocal capability battery in which the patient is asked to sustain a sung tone as steadily as possible, so as to detect tremor, or other kinds of vocal instability.
Adductory Spasmodic Dysphonia
AD-SD (1 of 2)
Sustained, clear phonation, standard light. Note vibratory blur of the vocal cord margins. The false vocal cords (lines) are in normal relation to the true vocal cords.
AD-SD (2 of 2)
Involuntary adductory spasm. Note that the false vocal cords suddenly over-close (arrows) as a result of the adductory spasm, and voice momentarily stops (along with vibratory blur).
