Correlation between the parameters of quadrilateral vowel and dysphonia severity in patients with traumatic brain injury

Dysarthria and dysphonia are common in patients with traumatic brain injury (TBI). Multiple factors may contribute to TBI-induced dysarthria, including poor vocalization, articulation, respiration, and/or resonance. Many patients suffer from dysarthria that persists after the onset of TBI, with negative effects on their quality of life. This study aimed to investigate the relationship between vowel quadrilateral parameters and Dysphoria Severity Index (DSI), which objectively reflects vocal function We retrospectively enrolled TBI patients diagnosed using computer tomography. Participants had dysarthria and dysphonia and underwent acoustic analysis. Praat software was used to measure vowel space area (VSA), formant centralization ratio (FCR), and the second formant (F2) ratio. For the 4 corner vowels (/a/,/u/,/i/, and/ae/), the resonance frequency of the vocal folds was measured and is shown as 2-dimensional coordinates for the formant parameters. Pear-son correlation and multiple linear regression analyses were performed between the variables. VSA showed a significant positive correlation with DSI/a/ (R = 0.221) and DSI/i/ (R = 0.026). FCR showed a significant negative correlation with DSI/u/ and DSI/i/. The F2 ratio showed a significant positive correlation with DSI/u/ and DSI/ae/. In the multiple linear regression analysis, VSA was found to be a significant predictor of DSI/a/ (β = 0.221, P = .030, R(2) = 0.139). F2 ratio (β = 0.275, P = .0.015) and FCR (β = −0.218, P = .029) was a significant predictor of DSI/u/ (R(2) = 0.203). FCR was a significant predictor of DSI/i/ (β = –0.260, P = .010, R(2) = 0.158). F2 ratio was a significant predictor of DSI/ae/ (β = 0.254, P = .013, R(2) = 0.154). Vowel quadrilateral parameters, such as VSA, FCR, and F2 ratio, may be associated with dysphonia severity in TBI patients.