Quantitative analysis of videokymography in normal and pathological vocal folds: a preliminary study

Videokymography (VKG) captures high-speed images of the vocal folds independently of the periodicity of the acoustic signal. The aim of this study was to preliminarily assess a software package that can objectively measure specific parameters of vocal fold vibration. From August 2009 until December 2010, we prospectively evaluated 40 subjects (Group A, 18 normal subjects; Group B, 14 patients with benign lesions of the middle third of the vocal fold, such as polyps and cysts; Group C, 8 patients treated by endoscopic excision of vocal fold benign lesions) by videoendoscopy, videolaryngostroboscopy, and VKG. A VKG camera was coupled to a 70° telescope and video was recorded during phonation. Images were objectively analyzed by a post-processing software tool (VKG-Analyser) with a user-friendly interface developed by our group. Different parameters were considered, including the ratio between the amplitude of the vibration of one vocal fold with respect to the contralateral (R(amp)), the ratio between the period of one vocal fold vibration and the opposite one (R(per)), and the ratio between the duration of the open and closed phase within a glottal cycle (R(oc)). Mean values for R(amp), R(per), and R(oc) in Group A were 1.05, 1.04, and 1.35, respectively; in Group B were 1.63, 0.92, and 0.97, respectively; and in Group C were 1.13, 0.91, and 1.85, respectively. Quantitative analysis of videokymograms by the herein presented tool, named VKG-Analyser, is useful for objective evaluation of the vibratory pattern in normal and pathologic vocal folds. Important future developments of this tool for the study of both physiologic and pathologic patterns of vocal fold vibration can be expected.