First results of clinical application of videokymography

Stroboscopy is based on the assumption that the vibration of the vocal folds is stable and regular. Irregular vibrations, which are common in voice pathology, cannot easily be studied and described in a reliable way. Videokymography overcomes most of these drawbacks.

The use of the recently invented videokymography for studying vocal fold vibrations in patients is introduced.

Videokymography, using a modified CCD-video camera, works in two modes: standard and high speed. In standard mode the vocal folds are displayed on a video monitor in the usual way, providing 50 images per second (or 60 in the National Television Standards Committee (NTSC) system). This is used for routine laryngoscopic and stroboscopic examination of the larynx. In high-speed mode (nearly 8000 images per second) only one line from the whole image is selected and displayed on the x-axis of the monitor; the y-axis represents the time dimension.

All kinds of vocal fold vibrations, including those leading to pathological rough, breathy, hoarse, or diplophonic voice productions can be observed. Videokymography visualizes small left-right asymmetries, open quotient differences along the glottis, lateral propagation of mucosal waves, and movements of the upper margin and, sometimes in the closing phase, the lower margin of the vocal folds.

Videokymography is advantageous for a more accurate diagnosis of voice disorders. Videokymography provides a simple way to study irregular vibrations of the vocal folds. Information is directly available for further processing and allows a first-time quantification of vibrations registered.