Correlations between swallowing function and acoustic vowel space in stroke patients with dysarthria

BACKGROUND: Dysphagia and dysarthria tend to coexist in stroke patients. Dysphagia can reduce patients' quality of life, cause aspiration pneumonia and increased mortality. OBJECTIVE: To evaluate correlations among swallowing function parameters and acoustic vowel space values in patients with stroke. METHODS: Data from stroke patients with dysarthria and dysphagia were collected. The formant parameter representing the resonance frequency of the vocal tract as a two-dimensional coordinate point was measured for the /a/, /ae/, /i/, and /u/vowels, and the quadrilateral vowel space area (VSA) and formant centralization ratio (FCR) were measured. Swallowing function was evaluated by a videofluoroscopic swallowing study (VFSS) using the videofluoroscopic dysphagia scale (VDS) and penetration aspiration scale (PAS). Pearson's correlation and linear regression analyses were used to assess the correlation of VSA and FCR to VDS and PAS scores. RESULTS: Thirty-one stroke patients with dysphagia and dysarthria were analyzed. VSA showed a negative correlation to VDS and PAS scores, while FCR showed a positive correlation to VDS score, but not to PAS score. VSA and FCR were significant factors for assessing dysphagia severity. CONCLUSIONS: VSA and FCR values were correlated with swallowing function and may be helpful in predicting dysphagia severity associated with stroke.