Vocal fold phase asymmetries in patients with voice disorders: a study across visualization techniques.

PURPOSE

To examine differences in vocal fold vibratory phase asymmetry judged from stroboscopy, high-speed videoendoscopy (HSV), and the HSV-derived playbacks of mucosal wave kymography, digital kymography, and a static medial digital kymography image of persons with hypofunctional and hyperfunctional voice disorders. Differences between the methods of visual judgments and objective measures of left-right phase asymmetry were assessed. The findings were compared with those from a previous study with vocally normal speakers.

METHOD

Forty-nine persons with voice disorders underwent stroboscopy and HSV. The HSV images were processed, resulting in 4 different spatial or kymographic displays. Two types of phase asymmetries, left-right and anterior-posterior, were visually rated. Objective measures of left-right phase asymmetry were obtained.

RESULTS

From stroboscopy, the HSV playback, and the HSV-derived playbacks, left-right phase symmetry was judged to be symmetrical in 41%, 32%, and 19% of cases, respectively. This difference in playbacks was not seen for anterior-posterior asymmetry. Correlation between visual judgments and objective measures was mild for stroboscopy and moderate to high for all HSV-based playbacks.

CONCLUSIONS

The use of kymography appears important for judgments of phase asymmetry. Stroboscopy appears to be sensitive, but possibly not specific, to phase asymmetries. Further development of objective measures is warranted for this feature.