Research in Vestibular Science

Original Articles

Unilateral Vestibulopathy Mimicking Inner Ear Ischemia Modeling Using Photothrombosis and Behavioral Assessment Using EthoVision: Min Seok Song, Min Young Lee, Ji Eun Choi, So-Young Chang, Jae-Hun Lee, John Patrick Cuenca, Nathaniel T. Carpena, Jae Yun Jung; Res Vestib Sci. 2023;22(4):112-119. Published online December 15, 2023; DOI: https://doi.org/10.21790/rvs.2023.22.4.112

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Abstract PDF: Objectives
Inner ear ischemic animal models using photochemical reactions have been devised in various ways. Localized vascular ischemia occurs with 532-nm laser irradiation after systemic rose bengal injection, a known photothrombotic mechanism. The aim of this study is to evaluate a photothrombosis-induced vestibulopathy mimicking behavioral changes in the inner ear ischemia model.
Methods
Seven-week-old male Spraque-Dawley rats were used. Animals were divided into three groups: control group (n=6), sham laser group (n=9), and laser group (n=9). To induce the photothrombosis, animals were injected with rose bengal into the femoral vein and then were irradiated with a 532-nm laser (175 mW for 900 seconds) via transtympanic membrane. To investigate the vestibulopathy after photothrombosis, the behavior tests (tail lift reflex test, air righting reflex test, rotarod test) were performed on the 1st, 3rd, and 7th days after surgery. Additionally, an open field test was conducted and analyzed using EthoVision XT (Noldus).
Results
The laser group exhibited significant behavioral change to mimic vestibulopathy in all assessments. Inducing photothrombosis with rose bengal caused severe gait instability, which precluded rotarod testing. In the tail lift reflex test, the laser group displayed vestibular dysfunction with a lower angle formation compared to the control rats. During the open field test, the laser group exhibited reduced mobility, a condition that persisted in the laser groups for 7 days.
Conclusions
Noninvasive laser irradiation using rose bengal and a 532-nm laser induces photothrombosis in the inner ear of animals, leading to the development of vestibulopathy mimicking imbalanced behavior.

Study on Platelet Indices in Benign Paroxysmal Positional Vertigo: Byeong Min Lee, Chae Dong Yim, Dong Gu Hur, Seong-Ki Ahn; Res Vestib Sci. 2021;20(4):141-146. Published online December 15, 2021; DOI: https://doi.org/10.21790/rvs.2021.20.4.141

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Abstract PDF: Objectives
Benign paroxysmal positional vertigo (BPPV) is one of the most common causes of dizziness. Even though the etiology of BPPV has been widely studied, the exact mechanism remains still unclear. One of the possible factors explaining the pathophysiology of BPPV is ischemia of vestibule. In the present study, we have focused on the platelet indices including mean platelet volume (MPV), platelet distribution width (PDW), and platelet crit (PCT) to assess a risk of vestibule ischemia causing BPPV.
Methods
From January 2021 to March 2021, a retrospective review was performed on 39 patients diagnosed with BPPV through vestibular nystagmography. For each platelet indices, a comparative analysis was conducted between the patient group and control group.
Results
There were no significant differences when the platelet, MPV, PDW, and PCT values were compared between the study and control group. Rather, the control group showed higher PDW value than the study group.
Conclusions
Ischemia of vestibule is one of the well-known causes of BPPV, but the current study showed that BPPV cannot be explained by the vestibule ischemia itself. Further studies are needed to identify the potential of ischemia regarding BPPV by approaching with other methods with a large study group.

Eye Movement Abnormalities and Neuroimaging Findings of Disequilibrium of Unknown Origin: Jae Yong Go, Jung Im Seok, Dong Kuck Lee; Res Vestib Sci. 2014;13(4):108-113.

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Abstract PDF: Background
and Objectives: Although disequilibrium is common type of dizziness in older people, it is sometimes difficult to identify a specific cause for this problem. The diffuse brain pathology including subcortical ischemia and atrophy can be a cause for patients with disequilibrium of unknown cause. Aim of this study is to identify the eye movements and neuroimaging features in patients with disequilibrium. Materials and Methods: We performed a prospective investigation in patients with disequilibrium of unknown cause. We collected information on demographic characteristics and clinical features of disequilibrium. The impact of dizziness on everyday life was assessed by 25-item dizziness handicap inventory (DHI). Vestibular function test (VFT) includes smooth pursuit, saccade, optokinetic nystagmus, and rotatory chair test. Subcortical white matter lesions and brain atrophy were graded from brain magnetic resonance image (MRI).
Results
This study included 14 patients (12 female and 2 male), aged between 64 and 84 years, mean age 74.01±6.02 years. The score of DHI was 39.4±11.8 (20?58). Eye movements were abnormal in 13 patients and normal in only one patient. The degree of subcortical ischemia was mild in 7, moderate in 4, and severe in 3 patients. Ventricular brain ratio was 0.23±0.03. However, there was no significant relationship between MRI findings and the degree of oculomotor alterations (result of VFT). Conclusion: Patients with disequilibrium of unknown cause are usually elderly women. Alterations in oculomotor movements and diffuse brain pathology including white matter lesions and atrophy were observed in patients with disequilibrium of unknown cause.

Comparison of Audiovestibular Dysfunction in Patients of Acute Unilateral Peripheral Vestibulopathy with and without Vascular Risk Factors: Jun Hyun Kim, Tae Kyeong Lee, Ki Bum Sung; Res Vestib Sci. 2014;13(4):96-101.

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Abstract PDF: Background
and Objectives: Etiology of acute unilateral peripheral vestibulopathy (AUPV) includes virus, ischemia, and autoimmune. As anatomical distribution is similar between vasculature and innervation, AUPV with vascular risk factors could be ischemic origin. We investigated the pattern of audiovestibular dysfunction to explore the influence of risk factors on AUPV. Materials and
Methods
We collected records of 162 AUPV patients from 2011 to 2013 who were admitted within 7 days from vertigo onset and diagnosed as AUPV by caloric test and neuro-otologic examination. Vascular risk factors are stroke history, hypertension, diabetes, body mass index ＞25, age ＞60, and vertebrobasilar stenosis. Bedside examination includes spontaneous nystagmus grade, head impulse test, head shaking test. Results of rotatory chair test (n=125), caloric test (n=162), cervical (n=33) and ocular (n=23) vestibular evoked myogenic potential (VEMP), subjective visual vertical (SVV) (n=91), and pure tone audiometry (PTA) (n=62) are collected. Results: Abnormalities of PTA are found more in patients with vascular risk factor than without any risk factor. Specifically, hypertension (p=0.008) and old age (p=0.025) are associated with PTA abnormality (p=0.006). Tilt angle of vertical is larger in risk factor group (p=0.019). The number of vascular risk factor correlates with abnormalities of PTA (p=0.025) and tilt angle of SVV. Results of bedside examination, rotatory chair test, caloric test, cervical and ocular VEMP are not associated with vascular risk factors. Conclusion: AUPV patients with vascular risk factors have more extensive involvement of audiovestibular function. Ischemic etiology may contribute to pathogenesis of extensive AUPV.

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