Quantitative Analysis of Unilateral and Bilateral Vocal Fold Immobility

Abstract

To analyze the correlation between clinical and video laryngoscopy findings for 89 patients with bilateral vocal fold immobility (BVFI), unilateral vocal fold immobility (UVFI), and healthy controls by quantitative analysis of normalized laryngeal outlet (NLO), bowing index (BI), and supraglottic compression (SGC). Laryngoscope pictures were taken by two reviewers, and all pictures were standardized by scaling and calibrating to the same width and height in Image J. Three reviewers used quantitative measures to calculate BI, NLO, and SGC in Image J. We assessed reliability for each measurement by two-factor analysis of variance (ANOVA) without replication to calculate the interclass correlation coefficient. Analysis was broken down for each measurement in each group of interest by using a one-way test. The total glottic area was obtained by calculating the normalized glottal gap area from each image of maximum glottal closure during phonation. Overall reliability of all the measurements was 0.69 (IQ 0.58-0.83). Mean NLO from UVFI, BVFI, and control groups differed significantly. There was no significant difference between control and BVFI. The total glottic area did not consistently predict normalized laryngeal outlet values. Mean normalized laryngeal outlet values of UVFI and BVFI were significantly smaller in the BVFI groups compared with controls and UVFI. BI values consistently predicted total glottic area in the BVFI group. Static SGC measurement did not predict a difference between groups. This is a reliable novel technique, which can be utilized in clinical settings. These measurements have clinical relevance for managing voice disorders. NLO is the most accurate measurement correlating with glottal incompetence. BI findings are sufficiently specific to identify between UVFI and BVFI.