Evaluation of Stroboscopic Signs

Abstract

Clinicians interpret the stroboscopic examination by systematically rating several parameters or "signs." This can be time consuming and experience dependent. The significance of each of these signs is unknown. Some signs may be redundant, whereas others may be more independent, thus reflecting a unique aspect of the exam assessment. We wanted to determine which stroboscopic signs are more independent and clinically relevant. This may lead to a more efficient and reliable method of stroboscopic exam evaluation. Retrospective. One hundred and eighty one consecutive adult patients with dysphonia of various pathologies were studied. Severity of dysphonia was judged, and a set of seven stroboscopic signs for each stroboscopic exam was rated by our voice team. A principal component factor analysis was performed, and the two factors that accounted for the most variance in the original rating data were determined. These two independent factors were then investigated for clinical usefulness. Several individual stroboscopic signs of vocal fold vibration correlated with the "Vibration Factor" (VF) (mucosal wave, amplitude, vibratory behavior, and periodicity) and the vocal fold edge correlated with the "Edge Factor" (EF). Scores for VF and EF were used to differentiate between general categories of vocal fold pathology and related to the severity of dysphonia. Severity of dysphonia correlated with the VF to a greater degree than the EF. Furthermore, these two factor scores could be accurately estimated using only three stroboscopic signs (amplitude, vibratory behavior, and edge). The results of the study support the concept that a small set of stroboscopic ratings is an adequate representation of the information derived from the original, more comprehensive sign rating protocol. A focused rating system may provide an efficient method for stroboscopic evaluation, contributing to the differentiation of various vocal fold pathologies and correlating to clinician ratings of severity of dysphonia.