Research in Vestibular Science

Volume 24 (2); June 2025

Review Articles

Outcome measures to assess and manage bilateral vestibulopathy in adults: a systematic review: Michaela de Kock, Tian Yuan, Elke Devocht, Nils Guinand, Angélica Pérez Fornos, Herman Kingma, Lisa van Stiphout, Florence Lucieer, David Robert Jay, Vincent van Rompaey, Raymond van de Berg; Res Vestib Sci. 2025;24(2):55-67. Published online June 15, 2025; DOI: https://doi.org/10.21790/rvs.2025.004

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Abstract PDF Supplementary Material: Bilateral vestibulopathy (BV) is a complex chronic condition characterized by a significantly reduced or absent function in both vestibular organs. Although the diagnostic criteria for BV have been established, the challenge arises when approaching BV management. To select appropriate outcome measures (OMs), it is essential first to identify all available measures. This systematic review aims to provide a comprehensive overview of the OMs reported in the literature for assessing and managing BV in adults. This review was performed in accordance with the PRISMA guidelines. The final set of studies was used for OM extraction. OM categories were identified and a categorization system was proposed. The frequency of use of OMs reported was conducted as an indication of reliance. Subsequently, the proposed OM categorization was combined with the International Classification of Functioning, Disability, and Health model. Extracted OMs were used a total of 2,118 times: 1,213 times for inclusion, and 905 times for evaluation purposes. Six main categories of OMs were identified. The vestibular category contained the most frequently used OMs, primarily for study inclusion. This was followed by motor-related and quality-of-life–related OMs, which were mainly used for study evaluation. Cognitive, mental well-being, and auditory OMs were the least investigated categories. Significant variability within OM categories was observed. This review highlights the variability in OMs for assessing and managing BV in the available literature. To mitigate this, a categorization system was proposed. This review marks an initial step toward establishing a standardized core set of OMs for assessing and managing BV.

Dizziness and neuro-otologic findings in neurodegenerative disorders: a review: Seunghee Na, Yun Jeong Hong, Seong-Hoon Kim, Eek-Sung Lee; Res Vestib Sci. 2025;24(2):68-78. Published online June 15, 2025; DOI: https://doi.org/10.21790/rvs.2024.026

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Abstract PDF: Eye movement abnormalities can provide valuable diagnostic insights across various neurodegenerative disorders. This review summarizes the characteristic oculomotor findings in different neurodegenerative conditions, focusing on cognitive disorders and parkinsonian syndromes. The neural control of eye movements involves complex networks across multiple cortical regions, including the frontal eye field, supplementary eye field, and dorsolateral prefrontal cortex, functioning in coordination with subcortical structures. In Alzheimer disease, patients exhibit impaired fixation with large saccadic intrusions, prolonged saccadic latency, and increased antisaccade errors, which correlate with cognitive decline. Frontotemporal dementia shows variant-specific patterns of oculomotor dysfunction, with behavioral variant particularly affecting antisaccade performance while maintaining the ability to self-correct errors. In parkinsonian syndromes, distinctive eye movement abnormalities aid in differential diagnosis. Idiopathic Parkinson disease typically presents with hypometric saccades and increased saccadic intrusions during fixation, which correlate with disease severity. Progressive supranuclear palsy characteristically shows early vertical saccade abnormalities and frequent macro–square-wave jerks. Multiple system atrophy demonstrates various central nystagmus patterns and perverted head-shaking nystagmus, while corticobasal degeneration presents with saccadic apraxia and asymmetric oculomotor abnormalities. While eye movement abnormalities can be nonspecific and overlap between conditions, careful evaluation of oculomotor function can provide important diagnostic clues, particularly for differentiating parkinsonian syndromes. Understanding these distinct patterns of oculomotor abnormalities provides critical insights into the underlying pathophysiology and serves as a valuable tool for differential diagnosis of neurodegenerative disorders.

Vestibulo-ocular reflex findings in key subtypes of hereditary cerebellar ataxia: a review: Jae-Myung Kim, Alexander Andrea Tarnutzer, Seung-Han Lee; Res Vestib Sci. 2025;24(2):79-88. Published online June 15, 2025; DOI: https://doi.org/10.21790/rvs.2025.003

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Abstract PDF: Vestibulo-ocular reflex (VOR) impairments are common in central vestibular disorders and may provide critical insights into disease-specific pathophysiology and diagnosis. Recent advances in quantitative VOR and oculomotor measurement techniques, such as video head impulse testing and video-oculography, have further enhanced the accuracy and efficiency of these assessments. This is particularly important in the field of hereditary cerebellar ataxia, where definitive diagnosis still depends on genetic testing due to significant overlap in clinical phenotypes and considerable variability. This review focuses on four representative subtypes selected based on both global prevalence and the predominance of vestibular dysfunction, as evaluated by quantitative assessments: spinocerebellar ataxia type 3 (SCA3), SCA6, Friedreich ataxia (FRDA), and cerebellar ataxia with neuropathy and vestibular areflexia syndrome (CANVAS). Quantitative vestibular assessments revealed distinct patterns of VOR impairment. SCA3 and CANVAS consistently show markedly reduced angular VOR (aVOR) gains across all stimulation frequencies and measurement techniques. In contrast, FRDA demonstrates aVOR impairments primarily during high-frequency stimuli, with inconsistent low-frequency responses. SCA6 is characterized by frequent high-frequency aVOR impairments, predominantly affecting horizontal and posterior canals, while low-frequency responses remain variable. Notably, aVOR suppression (VOR cancellation) is severely impaired in SCA6 and in approximately half of FRDA cases, but relatively preserved in SCA3 and CANVAS, offering a potential marker for differential diagnosis. An integrated assessment of vestibular and oculomotor findings may provide valuable diagnostic clues. This review aims to assist clinicians and researchers in understanding the characteristic VOR profiles of key hereditary cerebellar ataxias.

Understanding body composition in vestibular disorders: where do we stand? A narrative review: Seong-Hae Jeong, Eunjin Kwon; Res Vestib Sci. 2025;24(2):89-97. Published online June 15, 2025; DOI: https://doi.org/10.21790/rvs.2025.009

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Abstract PDF: Vestibular disorders significantly affect balance and spatial orientation, yet symptom severity varies greatly among patients with similar levels of vestibular impairment. Emerging evidence suggests that differences in body composition, specifically muscle mass, fat distribution, and bone density, may play crucial roles in modulating vestibular symptoms and overall functional outcomes. Sarcopenia, characterized by reduced muscle mass and strength, and conditions like osteopenia and osteoporosis have been independently linked to increased dizziness and imbalance, particularly in older adults. Experimental studies in animal models indicate vestibular system involvement in regulating muscle and bone metabolism via gravity-induced mechanisms, emphasizing vestibular-dependent molecular pathways. However, current clinical evidence remains preliminary, and further well-designed prospective studies are needed to clarify these relationships. This review synthesizes available insights into the interplay between vestibular function and body composition, highlights its clinical implications, and advocates for integrated management strategies, while emphasizing the importance of ongoing rigorous research.

Original Article

Inner ear uptake of fluorescent gentamicin in neonatal mice: an experimental animal study: Jihye Rhee, Dong Woo Nam, Sung Joong Moon, Ja-Won Koo; Res Vestib Sci. 2025;24(2):98-106. Published online June 15, 2025; DOI: https://doi.org/10.21790/rvs.2025.012

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Abstract PDF: Objectives
This study aimed to investigate whether systemic administration of fluorescently labeled gentamicin (gentamicin-Texas Red, GTTR) results in differential inner ear uptake during postnatal maturation of the blood-labyrinth barrier (BLB) in neonatal mice.
Methods
Neonatal C57BL/6 mice were intraperitoneally injected with GTTR at postnatal day 7 (P7), 21 (P21), or 35 (P35). Cochlear and renal tissues were harvested 60 minutes after injection and examined via confocal microscopy. Fluorescence intensity of GTTR in cochlear structures—including marginal cells, strial tissues, basal cells, spiral ligament, and hair cells—was quantified using ImageJ. Renal proximal tubules served as systemic uptake controls.
Results
GTTR uptake was significantly higher in cochlear lateral wall structures and hair cells of P7 mice compared to P35 mice (p<0.01). No significant differences in fluorescence were observed in the renal proximal tubules across age groups. Mice injected with unconjugated Texas Red showed negligible fluorescence in all tissues, confirming specific uptake of GTTR.
Conclusions
Inner ear uptake of aminoglycosides is markedly increased prior to full maturation of the BLB in neonatal mice. These findings suggest that immature cochlear barriers in early postnatal stages may enhance aminoglycoside entry into sensory hair cells, highlighting the need for cautious use of these antibiotics in premature infants.

Case Reports

Positional nystagmus in pneumolabyrinth: a case report: Dong-Han Lee, Do-Won Kwon, Minho Jang, Jung Eun Shin, Chang-Hee Kim; Res Vestib Sci. 2025;24(2):107-112. Published online June 15, 2025; DOI: https://doi.org/10.21790/rvs.2025.011

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Abstract PDF Supplementary Material: This report describes a patient with left-sided pneumolabyrinth following a temporal bone fracture and demonstrates characteristic positional nystagmus observed in this condition while discussing its mechanism. A previously healthy 38-year-old man presented with left-sided hearing loss, tinnitus, and positional vertigo after blunt head trauma. Temporal bone computed tomography revealed pneumolabyrinth in the ampulla of the left lateral semicircular canal (LSCC). Pure tone audiometry showed mixed hearing loss on the left (bone, 13.8 dB; air, 42.5 dB). Video Frenzel examination revealed direction-changing positional nystagmus: persistent left-beating nystagmus in the bow position, right-beating nystagmus upon moving from bowing to leaning, and persistent left-beating nystagmus in the left head-roll position only. We propose that in pneumolabyrinth involving the LSCC, changes in head position shift the air bubble, generating a buoyant force that indents the endolymphatic membrane and deflects the cupula, producing positional nystagmus. The direction of nystagmus may vary depending on the bubble’s location.

Positional downbeat nystagmus in metronidazole-induced cerebellar toxicity: a case report: Hyesoo Kwon, Hyun Ah Kim; Res Vestib Sci. 2025;24(2):113-116. Published online June 15, 2025; DOI: https://doi.org/10.21790/rvs.2025.015

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Abstract PDF Supplementary Material: We report a case of metronidazole-associated cerebellar toxicity presenting with positional downbeat nystagmus, a relatively uncommon but clinically significant manifestation. A 61-year-old man developed ataxia, dysarthria, and positional nystagmus after nearly 2 months of metronidazole treatment for a brain abscess in the frontal lobe. Brain magnetic resonance imaging (MRI) showed symmetrical T2-weighted/fluid-attenuated inversion recovery hyperintensities in the dentate nuclei and tectal plate. These findings, along with prolonged use of intravenous metronidazole, supported the diagnosis of metronidazole-induced cerebellar toxicity. Discontinuation of the drug led to marked clinical and radiologic improvement. This case highlights the importance of recognizing positional downbeat nystagmus as a potential early indicator of metronidazole-induced neurotoxicity. Early identification of this oculomotor pattern may prompt timely imaging and cessation of the offending agent, potentially preventing irreversible neurologic damage.

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