Interleukin-6 Receptor Polymorphisms Contribute to the Neurological Status of Korean Patients with Ischemic Stroke.

To investigate the contribution of the interleukin-6 receptor (IL-6R) gene single nucleotide polymorphisms (SNPs) to the neurological status of Korean patients with ischemic stroke (IS), two SNPs of the IL-6R gene (rs4845617, 5 UTR; rs2228144, Ala31Ala) were selected. IS patients were classified into clinical phenotypes according to two well-defined scores: the National Institutes of Health Stroke Survey (NIHSS) and the Modified Barthel Index scores. There were 121 IS patients and 291 control subjects. The SNP rs4845617 significantly contributed to the neurological status of patients with IS (P = 0.011 in codominant model 2, P = 0.006 in recessive model, and P = 0.008 in log-additive model). Allele frequencies of rs4845617 and rs2228144 demonstrated no significant difference in IS patients and controls. The AG and GG haplotypes differed between the NIHSS 1 (NIHSS scores < 6) group and the NIHSS 2 (NIHSS scores ≥ 6) group in patients with IS (P = 0.014, P = 0.0024). These results suggest that rs4845617 of the IL-6R gene is associated with the neurologic status of Korean patients with IS.

Erratum: Inpatient Stroke Rehabilitation Outcomes in Korea Derived from the Korean Brain Rehabilitation Centers' Online Database System for the Years 2007 to 2011.

[This corrects the article on p. 644 in vol. 30, PMID: 25931798.].

Inpatient stroke rehabilitation outcomes in Korea derived from the Korean Brain Rehabilitation Centers' online database system for the years 2007 to 2011.

The purpose of this report was to provide information for patients receiving inpatient rehabilitation after stroke and to identify the possible factors influencing functional outcome after inpatient rehabilitation. Stroke patients (n = 5,212) who were discharged from the Departments of Rehabilitation Medicine (RM) of university hospitals and rehabilitation hospitals from 2007 through 2011 were participants. Prevalence, age, transfer time after onset, length of stay (LOS), functional status at admission and discharge were analyzed. In all stroke subjects, cerebral infarctions (67%) were more common than hemorrhages. Cerebral infarctions in the middle cerebral artery territory were most common, while the basal ganglia and cerebral cortex were the most common areas for hemorrhagic stroke. The LOS decreased from 45 to 28 days. Transfer time after onset decreased from 44 to 30 days. Shorter transfer time after onset was correlated with better discharge functional status and shorter LOS. Initial functional status was correlated with discharge functional status. In ischemic stroke subtypes, cerebellar and brainstem strokes predicted better outcomes, while strokes with more than one territory predicted poorer outcomes with more disabilities. In hemorrhagic stroke subtypes, initial and discharge functional status was the lowest for cortical hemorrhages and highest for brainstem hemorrhages. This report shows that LOS and transfer time after onset has been decreased over time and initial functional status and shorter transfer after onset are predictors of better functional outcome at discharge.

Association between BH3 interacting domain death agonist (BID) gene polymorphism and ossification of the posterior longitudinal ligament in Korean population.

The purpose of this study was to investigate single nucleotide polymorphisms (SNPs) of the BH3 interacting domain death agonist (BID) gene as a risk factor in Korean patients with ossification of the posterior longitudinal ligament (OPLL). To investigate the genetic association, two coding SNPs (rs8190315, Ser10Gly; rs2072392, Asp60Asp) of BID were genotyped in 157 OPLL patients and 209 control subjects. SNPStats, SNPAnalyzer Pro, Helixtree, and Haploview 4.2 programs were used for association analysis. Multiple logistic regression models (codominant, dominant, and recessive) were calculated for the odds ratios (ORs), 95 % confidence intervals (CIs), and corresponding P values. For multiple testing, Bonferroni correction was performed. After Bonferroni correction, genotype analysis of both rs8190315 and rs2072392 showed association between the OPLL group and the control group in the codominant model (P = 0.042, OR 1.86, 95 % CI 1.10-3.15). A complete linkage disequilibrium block was estimated between the two SNPs. Both of the G allele of rs8190315 and C allele of rs2072392 were strongly associated with an increased risk in the development of OPLL (P = 0.0052, OR 2.66, 95 % CI 1.51-4.68). These results suggest that BID is associated with OPLL, and both the G allele of a missense SNP (rs8190315, Ser10Gly) and C allele of a synonymous SNP (rs2072392, Asp60Asp) are risk factors for the development of OPLL in Korean population.

NADPH oxidase 1 mediates α-synucleinopathy in Parkinson's disease.

Accumulation of misfolded α-synuclein is the pathological hallmark of Parkinson's disease (PD). Nevertheless, little is known about the mechanism contributing to α-synuclein aggregation and its further toxicity to dopaminergic neurons. Since oxidative stress can increase the expression and aggregation levels of α-synuclein, NADPH oxidases (Noxs), which are responsible for reactive oxygen species generation, could be major players in α-synucleinopathy. Previously, we demonstrated that Nox1 is expressed in dopaminergic neurons of the PD animal models as well as postmortem brain tissue of PD patients, and is responsible for oxidative stress and subsequent neuronal degeneration. Here, using paraquat (PQ)-based in vitro and in vivo PD models, we show that Nox1 has a crucial role in modulating the behavior of α-synuclein expression and aggregation in dopaminergic neurons. We observed in differentiated human dopaminergic cells that Nox1 and α-synuclein expressions are increased under PQ exposure. Nox1 knockdown significantly reduced both α-synuclein expression and aggregation, supporting the role of Nox1 in this process. Furthermore, in rats exposed to PQ, the selective knockdown of Nox1 in the substantia nigra, using adeno-associated virus encoding Nox1-specific shRNA, largely attenuated the PQ-mediated increase of α-synuclein and ubiquitin expression levels as well as α-synuclein aggregates (proteinase K resistant) and A11 oligomers. Significant reductions in oxidative stress level and dopaminergic neuronal loss were also observed. Our data reveal a new mechanism by which α-synuclein becomes a neuropathologic protein through Nox1-mediated oxidative stress. This finding may be used to generate new therapeutic interventions that slower the rate of α-synuclein aggregation and the progression of PD pathogenesis.

Nanostructural and nanomechanical responses of collagen fibrils in the collagenase-induced Achilles tendinitis rat model.

Achilles tendons are vulnerable to acute or chronic injuries that lead to inflammation. We investigated nanostructural and nanomechanical changes in collagen fibrils from rat Achilles tendons over a period of 9 weeks after injury using atomic force microscopy (AFM). To evaluate the nanostructural changes in Achilles tendons, we measured the diameter and D-banding of collagen fibrils by AFM. And the adhesion forces, which were related to cross-linking of collagen, were calculated from the retraction process of a force-distance curve. We successfully observed the time course of changes in collagen fibrils during healing using AFM. The diameters and D-banding in healed tendons were similar to those of uninjured tendons at 9 weeks after injury, but the adhesion forces remained different from those of uninjured tendons. Our AFM results depicted the minute changes in Achilles tendon surface by natural healing quite well, even drawbacks to naturally healed tendon. Understanding changes in collagen cross-linking and structure while healing will lead to better understanding of healing mechanisms and subsequent improvements in treatment. And AFM can be applied as powerful tool to evaluate structural and property changes in collagen fibrils before and after injury and/or treatment in Achilles tendon.

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/ (ß = 0.221, P  = .030, R 2  = 0.139). F2 ratio (ß = 0.275, P  = .0.015) and FCR (ß = -0.218, P  = .029) was a significant predictor of DSI/u/ (R 2  = 0.203). FCR was a significant predictor of DSI/i/ (ß = -0.260, P  = .010, R 2  = 0.158). F2 ratio was a significant predictor of DSI/ae/ (ß = 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.

Serum vitamin D levels and peak cough flow in patients with subacute ischemic stroke.

Aspiration pneumonia is a major, potentially fatal complication after ischemic stroke. Decreased coughing function is a significant risk factor for aspiration in ischemic stroke survivors. Peak cough flow (PCF) is a useful tool for assessing cough function. Vitamin D deficiency is frequent after ischemic stroke and is linked to a variety of muscle functions and physical activities. There has been no investigation of the correlation between vitamin D levels and PCF in ischemic stroke survivors. This study aimed to examine the relationship between serum vitamin D levels and PCF in patients with ischemic stroke. Patients with ischemic stroke who underwent PCF evaluation and serum vitamin D level measurements within 1 month of onset were retrospectively recruited. The association between PCF parameters and serum vitamin D levels was also analyzed. In total, 142 patients with ischemic stroke were included. PCF parameters and serum vitamin D levels were found to be significantly correlated. Moreover, serum vitamin D levels were shown to be a significant predictor of PCF parameters. Serum vitamin D levels were related to PCF parameters in patients with ischemic stroke. In addition, serum vitamin D level may serve as a predictor of coughing function in patients with ischemic stroke.

Assessing the effect of transcranial magnetic stimulation on peak cough flow in patients with supratentorial cerebral infarction: A retrospective cohort study.

Respiratory dysfunction following supratentorial cerebral infarction leads to pneumonia and is a major cause of mortality. Decreased voluntary cough function impairs the ability to clear mucus or secretions from the airways and increases the risk of aspiration pneumonia. Peak cough flow (PCF) is one of the objective tools for evaluating voluntary cough function. Repetitive transcranial magnetic stimulation (rTMS) could be applied to the respiratory motor cortex to improve respiratory function. Little is known about the effect of rTMS on PCF in patients with supratentorial cerebral infarction during the subacute period. This study aimed to determine whether rTMS treatment could improve PCF in patients with supratentorial cerebral infarction. We retrospectively recruited patients with subacute supratentorial cerebral infarction who underwent a PCF test. The rTMS group received a combination of rTMS treatment for 2 weeks and conventional rehabilitation for 4 weeks. However, the control group underwent only conventional rehabilitation for 4 weeks. PCF tests were performed before and after treatment and the results were compared between the 2 groups. In total, 145 patients with supratentorial cerebral infarctions were recruited. The PCF parameters before and after treatment increased in both the rTMS and control groups. However, the rTMS group showed a greater increase in PCF values compared with the control group. In patients with supratentorial cerebral infarction, the combination of conventional rehabilitation and rTMS in the subacute period may be helpful in improving voluntary cough function compared with conventional rehabilitation alone.

The Effect of Robot-Assisted Training on Arm Function, Walking, Balance, and Activities of Daily Living After Stroke: A Systematic Review and Meta-Analysis.

This meta-analysis aimed to compare the effects of robot-assisted training (RAT) with those of conventional therapy (CT), considering the potential sources of heterogeneity in the previous studies. We searched three international electronic databases (MEDLINE, Embase, and the Cochrane Library) to identify relevant studies. Risk of bias assessment was performed using the Cochrane's Risk of Bias 1.0 tool. The certainty of the evidence was evaluated using the Grading of Recommendations, Assessment, Development, and Evaluations method. The meta-analyses for each outcome of the respective domains were performed using 24 randomized controlled trials (RCTs) on robot-assisted arm training (RAAT) for arm function, 7 RCTs on RAAT for activities of daily living (ADL), 12 RCTs on robot-assisted gait training (RAGT) for balance, 6 RCTs on RAGT for walking, and 7 RCTs on RAGT for ADL. The random-effects model for the meta-analysis revealed that RAAT has significant superiority over CT in improving arm function, and ADL. We also showed that RAGT has significant superiority over CT in improving balance. Our study provides high-level evidence for the superiority of RAT over CT in terms of functional recovery after stroke. Therefore, physicians should consider RAT as a therapeutic option for facilitating functional recovery after stroke.

Nutritional Biomarkers as Predictors of Dysphonia Severity in Patients with Ischemic Stroke.

Dysphonia and malnutrition are major problems in patients who have suffered an ischemic stroke. Tools to assess dysphonia severity include the dysphonia severity index (DSI) and maximum phonation time (MPT). This study aimed to investigate whether the nutritional biomarkers transferrin, albumin, and prealbumin could be predictors of dysphonia severity. A retrospective analysis was conducted between January 2018 and October 2022. A total of 180 patients who had suffered an ischemic stroke were included. Serum transferrin, albumin, and prealbumin levels were significantly correlated with DSI and MPT levels. In a multiple regression analysis, prealbumin and transferrin were significant predictors of DSI, whereas only prealbumin was a significant predictor of MPT. Serum transferrin, albumin, and prealbumin levels in patients who have suffered an ischemic stroke may correlate with dysphonia severity as assessed using DSI and MPT. These results may provide objective evidence that nutritional biomarkers affect dysphonia severity.

Association Between Clinical Symptoms, Electrodiagnostic Findings, Clinical Outcome, and Prodromal Symptoms in Patients With Bell's Palsy.

OBJECTIVE: This study aimed to determine which prodromal symptoms frequently occur in patients with Bell's palsy and evaluate the association between these symptoms and clinical severity of paresis or the severity of facial nerve injury. MATERIALS AND METHODS: The study included 86 patients with Bell's palsy between August 2018 and April 2020. Severity levels of Bell's palsy and facial nerve damage were evaluated using the House-Brackmann (H-B) grading scale and electrodiagnostic study, respectively. Subsequently, a self-reported questionnaire on prodromal symptoms was administered. To assess the degree of recovery, the H-B grade was reported at 9 weeks and 6 months after the onset of paralysis. RESULTS: The most common prodromal symptoms were postauricular pain, sensory decline in the tongue, headache on the affected side, myalgia, facial sensory decline on the affected side, taste impairment, and dry eye. Taste impairment was significantly correlated with severe facial paralysis reported at 9 weeks after onset (P < .05) and was not related to the severity of paresis assessed at initial examination or 6 months after onset or on electrodiagnostic findings. CONCLUSIONS: The prodromal symptoms of Bell's palsy were not associated with the severity of facial nerve injury in an electrodiagnostic study. Taste impairment was related to clinical severity of paralysis at subacute stage, 9 weeks after onset, but it was not associated with long-term prognosis.

A Randomized, Double-Blind, Active Control, Multicenter, Phase 3 Study to Evaluate the Efficacy and Safety of Liztox® versus Botox® in Post-Stroke Upper Limb Spasticity.

Botulinum toxin type A (BTX-A) injection is a commonly used therapeutic intervention for upper limb spasticity in stroke patients. This study was designed as a randomized, active-drug-controlled, double-blind, multicenter, phase 3 clinical trial to evaluate the safety and efficacy of Liztox® in comparison to onabotulinum toxin A (Botox®) for individuals with post-stroke upper limb spasticity. The primary outcome was the alteration in wrist flexor muscle tone from the initial assessment to the fourth week, evaluated using the modified Ashworth scale (MAS). Secondary outcomes included MAS score changes for the wrist at weeks 8 and 12 from baseline; MAS score changes for finger and elbow flexors; and changes in the Disability Assessment Scale (DAS), Subject's Global Assessment (SGA), the Investigator's Global Assessment (IGA), and Caregiver Burden Scale (CBS) at weeks 4, 8, and 12 from baseline. The MAS score for wrist flexor spasticity decreased by -1.14 ± 0.59 in the Liztox® group and -1.22 ± 0.59 in the Botox® group from baseline to week 4. The difference [97.5% confidence interval (CI)] between the test and control groups was 0.08 [-∞, 0.26], confirming the non-inferiority of the test group compared to the control group. Furthermore, there were consistent improvements in the IGA, SGA, and CBS scores across all assessment intervals, with no statistically significant variances detected between the two groups. No safety-related concerns were reported during the study. In conclusion, Liztox® injection proved to be a secure and efficacious intervention for managing upper extremity spasticity in post-stroke patients.

Clinical Practice Guideline for Stroke Rehabilitation in Korea-Part 1: Rehabilitation for Motor Function (2022).

This clinical practice guideline (CPG) is the fourth edition of the Korean guideline for stroke rehabilitation, which was last updated in 2016. The development approach has been changed from a consensus-based approach to an evidence-based approach using the Grading of Recommendations Assessment Development and Evaluation (GRADE) method. This change ensures that the guidelines are based on the latest and strongest evidence available. The aim is to provide the most accurate and effective guidance to stroke rehabilitation teams, and to improve the outcomes for stroke patients in Korea. Fifty-five specialists in stroke rehabilitation and one CPG development methodology expert participated in this development. The scope of the previous clinical guidelines was very extensive, making it difficult to revise at once. Therefore, it was decided that the scope of this revised CPG would be limited to Part 1: Rehabilitation for Motor Function. The key questions were selected by considering the preferences of the target population and referring to foreign guidelines for stroke rehabilitation, and the recommendations were completed through systematic literature review and the GRADE method. The draft recommendations, which were agreed upon through an official consensus process, were refined after evaluation by a public hearing and external expert evaluation.

Korean Brain Rehabilitation Registry for rehabilitation of persons with brain disorders: annual report in 2009.

This first annual report provides a description of patients discharged from rehabilitation facilities in Korea based on secondary data analysis of Korean Brain Rehabilitation Registry V1.0 subscribed in 2009. The analysis included 1,697 records of patients with brain disorders including stroke, traumatic brain injury, brain tumor and other disorders from 24 rehabilitation facilities across Korea. The data comprised 1,380 cases of stroke, 104 cases of brain injury, 55 cases of brain tumor, and 58 cases of other brain diseases. The functional status of each patient was measured using the Korean version of the Modified Barthel Index (KMBI). The average change in the KMBI score was 15.9 for all patients in the inpatient rehabilitation facility. The average length of stay for inpatient rehabilitation was 36.9 days. The transfer rates to other hospitals were high, being 62.4% when all patients were considered. Patients with brain disorders of Korea in 2009 and measurable functional improvement was observed in patients. However, relatively high percentages of patients were not discharged to the community after inpatient rehabilitation. Based on the results of this study, consecutive reports of the status of rehabilitation need to be conducted in order to provide useful information to many practitioners.

Effects of extracorporeal shockwave therapy on nanostructural and biomechanical responses in the collagenase-induced Achilles tendinitis animal model.

The aim of this study was to quantitatively investigate the effects of extracorporeal shockwave therapy (ESWT) on the nanostructure and adhesion force of collagen fibrils in a rat model of collagenase-induced Achilles tendinitis (CIAT) using histology and atomic force microscopy. A total of 45 rats were divided into experimental groups of three rats each: a control group, 27 CIAT rats with nine time points, and 15 ESWT rats with five time points. Progressive changes in nanostructure including the fibrillary diameter and D-periodicity, and biomechanical properties including the fibrillary adhesion forces in each healing phase were investigated over a 5-week period after collagenase injection. On postoperative day 3, CIAT rats showed granulomatous tissue associated with subacute inflammation, and a deterioration in nanostructure and mechanical properties compared to controls. On postoperative day 12, the ESWT group showed increased vascularity, fibroblastic activity, lymphocyte and plasma cell infiltration, dense histocytes, and disorganization of the fibers compared to the CIAT group. The ESWT group showed and improvement in nanostructure and mechanical properties compared to controls, while the CIAT group showed a deterioration in nanostructure and mechanical properties compared to controls. On postoperative day 26, the ESWT group showed 30% inflamed tissue and 70% fibrotic tissue, while the CIAT group showed chronic inflammation. By the end of the experiments, in both groups the changes had reversed and the tissues were similar in appearance to those in the control group. Following ESWT the deformed and irregular collagen network returned to a well-aligned normal collagen network nanostructure. These results suggest that ESWT may promote the healing response in Achilles tendinitis.

Vitamin D level in relation to phonetic function among subacute stroke patients.

There are many stroke patients with decreased phonation ability. Vitamin D is associated with weakness in muscle power and a decreased function of activity and is often accompanied by a deficiency of serum vitamin D in stroke patients. This study was conducted to evaluate the correlation between serum vitamin D level and phonetic function in subacute stroke patients. Among subacute stroke patients, patients with dysphonia were retrospectively recruited. Phonation function was assessed by acoustic analysis using the dysphonia severity index (DSI) and maximum phonation time for 4 corner vowels/a/,/i/,/u/, and/ae/. As a statistical method, the relationships of vitamin D levels with the maximum phonation time and DSI were evaluated using Pearson's correlation analysis and linear regression analysis. A total of 32 stroke patients with dysphonia were assessed. A positive correlation was found between vitamin D levels and the DSI of /a/, /u/, /i/, and/ae/. The DSI of/u/ was significantly lower in the group with vitamin D deficiency. Vitamin D level was associated with phonation function and its deficiency may be a factor in predicting phonation severity in stroke patients.

Association of Depressive and Somatic Symptoms with Heart Rate Variability in Patients with Traumatic Brain Injury.

Depressive and somatic symptoms are common after traumatic brain injury (TBI). Depression after TBI can relate to worsened cognitive functioning, functional impairment, higher rates of suicide attempts, and larger health care costs. Heart rate variability (HRV) represents the activity of the autonomic nervous system (ANS), which regulates almost all vascular, visceral, and metabolic functions. Several studies show a correlation between HRV, depression, and somatic symptoms in other diseases. However, studies on autonomic dysfunction, depression, and somatic symptoms in TBI patients are lacking. This study investigated the association between reduced ANS function, depression, and somatic symptoms in TBI patients. We retrospectively recruited 136 TBI patients who underwent 24 h ambulatory Holter electrocardiography to measure autonomic dysfunction within 1 month of onset. Patients who used BDI and PHQ-15 to evaluate depressive and somatic symptoms were included. Using Pearson's correlation analysis and multiple linear regression, the association between HRV parameters and BDI and PHQ-15 was determined. The HRV parameters and BDI and PHQ-15 showed statistical significance. In addition, HRV was shown to be a significantly associated factor of BDI and PHQ-15. HRV was associated with depressive and somatic symptom severity in TBI patients. Additionally, autonomic dysfunction may serve as an associated factor of depressive and somatic symptoms in patients with TBI.

Nutritional Biomarkers and Heart Rate Variability in Patients with Subacute Stroke.

Malnutrition and autonomic dysfunction are associated with poor outcomes, mortality, and psychological problems after stroke. Relevant laboratory biomarkers include serum albumin, prealbumin, and transferrin. Heart rate variability (HRV), a noninvasive measurement, can objectively measure autonomic nervous system (ANS) function. The relationship between HRV and nutritional biomarkers in stroke patients has not been studied. This study aimed to examine the relationship between nutritional biomarkers and HRV parameters in stroke patients. We retrospectively recruited 426 patients with subacute stroke who were examined for nutritional biomarkers, such as serum albumin, prealbumin, and transferrin, and underwent 24 h ambulatory Holter electrocardiography. Patients were divided into groups according to their nutritional biomarker status. Differences in HRV parameters between nutritional biomarker-deficient and normal groups were assessed. Pearson's correlation and multiple regression analyses were used to verify the relationship between HRV parameters and nutritional biomarkers. HRV parameters were significantly lower in the nutritional biomarker-deficient groups. In addition, there was a significant association between HRV parameters and nutritional biomarkers. Serum albumin, prealbumin, and transferrin levels were associated with ANS function, as measured by HRV, and their deficiency may be a predictive factor for the severity of ANS dysfunction in stroke patients.

Destruction of Vowel Space Area in Patients with Dysphagia after Stroke.

Dysphagia is associated with dysarthria in stroke patients. Vowel space decreases in stroke patients with dysarthria; destruction of the vowel space is often observed. We determined the correlation of destruction of acoustic vowel space with dysphagia in stroke patients. Seventy-four individuals with dysphagia and dysarthria who had experienced stroke were enrolled. For /a/, /ae/, /i/, and /u/ vowels, we determined formant parameter (it reflects vocal tract resonance frequency as a two-dimensional coordinate point), formant centralization ratio (FCR), and quadrilateral vowel space area (VSA). Swallowing function was assessed using the videofluoroscopic dysphagia scale (VDS) during videofluoroscopic swallowing studies. Pearson's correlation and linear regression were used to determine the correlation between VSA, FCR, and VDS. Subgroups were created based on VSA; vowel space destruction groups were compared using ANOVA and Scheffe's test. VSA and FCR were negatively and positively correlated with VDS, respectively. Groups were separated based on mean and standard deviation of VSA. One-way ANOVA revealed significant differences in VDS, FCR, and age between the VSA groups and no significant differences in VDS between mild and moderate VSA reduction and vowel space destruction groups. VSA and FCR values correlated with swallowing function. Vowel space destruction has characteristics similar to VSA reduction at a moderate-to-severe degree and has utility as an indicator of dysphagia severity.