Frame by frame analysis of glottic insufficiency using laryngovideostroboscopy.

OBJECTIVES/HYPOTHESIS: Glottic insufficiency (GI) can be either grossly obvious or subtle in its presentation. Subtle GI is demonstrated by various Laryngovideostroboscopic (LVS) clues, including complete but "short" phase closure of the true vocal folds (VFs) during the glottic cycle. We used the frame by frame analysis (FBFA) technique to evaluate its effectiveness in objectively contributing to the diagnosis of subtle GI in patients with atrophic and/or paretic VFs. This article intends to formally present the methods and intentions of the FBFA technique and report our findings using FBFA on subjects with clinically diagnosed GI and normal volunteers.

STUDY DESIGN: Retrospective review and demonstration of technique.

METHODS: Forty-four subjects with a prior clinical diagnosis of true VF atrophy (25/44) and/or paresis (19/44) and five normal volunteers were identified. Using the FBFA technique, each subject's average percentage of closed frames per glottic cycle was recorded.

RESULTS: Subjects with atrophy spent 32.4% of the frames of the glottic cycle in the closed phase, subjects with paresis spent 35.7% of the frames closed, and normal subjects spent 50.2% of the frames closed.

CONCLUSIONS: FBFA appears to be a simple objective method for the novice or experienced LVS interpreter, by which one can suspect subtle GI. Because of the inherent physical properties by which LVS gives an "illusionary" representation of the glottic cycle, the FBFA technique remains a theoretical tool. Future studies using high-speed digital imaging are needed to validate this useful technique.