Compensation of Vestibular Function and Plasticity of Vestibular Nucleus after Unilateral Cochleostomy.

Dizziness and vertigo frequently occur after cochlear implantation (CI) surgery, particularly during the early stages. It could recover over time but some of the patients suffered from delayed or sustained vestibular symptoms after CI. This study used rat animal models to investigate the effect of unilateral cochleostomy on the vestibular organs over time. Twenty-seven Sprague Dawley rats underwent cochleostomy to evaluate the postoperative changes in hearing threshold, gain and symmetry of the vestibular ocular response, overall balance function, number of hair cells in the crista, and the c-Fos activity in the brainstem vestibular nucleus. Loss of vestibular function was observed during the early stages, but function recovered partially over time. Histopathological findings demonstrated a mild decrease in vestibular hair cells numbers. Increased c-Fos immunoreactivity in the vestibular nucleus, observed in the early stages after cochleostomy, decreased over time. Cochleostomy is a risk factor for peripheral vestibular organ damage that can cause functional impairment in the peripheral vestibular organs. Altered vestibular nucleus activity may be associated with vestibular compensation and plasticity after unilateral cochleostomy.

Distinct vestibular phenotypes in DFNA9 families with COCH variants.

Mutations of COCH can cause hearing loss and less frequently vestibular symptoms. However, vestibular phenotypes, especially in terms of the location of specific variants are not well documented yet. In this study, a retrospective and prospective cohort survey was performed in two tertiary referral hospitals to demonstrate vestibular phenotypes of DFNA9 subjects with a focus on the relationship with the location of COCH mutations. Two DFNA9 subjects were recruited from the previously collected cohort, each segregating p.G38D and p.C162Y of the COCH gene. Another two DFNA9 families were newly detected by targeted resequencing of known 129 deafness genes (TRS-129). These two families segregated the p.G38D variant of the COCH gene as the causative mutation, making p.G38D the most frequent COCH mutation in our Korean cohorts. Regarding the detailed clinical phenotype of the four DFNA9 families with documented vestibular phenotypes, we were able to classify them into two groups: one (p.C162Y variant) with a Meniere's disease (MD)-like phenotype and the other three (p.G38D variant) with significant bilateral vestibular loss without any definite MD symptoms. Distinct vestibular phenotypes depending on the location of COCH mutations were demonstrated, and this study correlates a genotype of p.G38D in COCH to the phenotype of bilateral total vestibular loss, therefore expanding the vestibular phenotypic spectrum of DFNA9 to range from bilateral vestibular loss without episodic vertigo to MD-like features with devastating episodic vertigo. In addition, the p.G38D variant of the COCH gene is suggested to be a frequent cause of progressive audiovestibular dysfunction in Koreans eventually requiring cochlear implantation.

Comparisons in Outcome and Subject Comfort between Rotation Chair Systems.

BACKGROUND AND OBJECTIVES: A rotation chair test has been used to evaluate the function of the horizontal semicircular canals. Currently, two chair systems according to the presence of cylindrical darkroom are used in a clinic setting. However, it has not been thoroughly investigated whether one system is superior to the other system or not. In this study, we aimed to compare test outcomes and subject convenience between two systems. SUBJECTS AND METHODS: Twenty subjects with no history of otologic disease were enrolled. Subjects were tested with two systems: system [A] with a cylindrical chamber and system [B] with no chamber. The results of sinusoidal harmonic acceleration (SHA), step velocity (SV), and visual fixation (VFX) tests were compared between the systems. Subject convenience was assessed with a questionnaire survey and results were compared between the systems. RESULTS: There were no significant differences in gain or asymmetry in SHA test between the systems. However, the phase of system [A] was significantly lower than that of system [B] at 0.16 Hz. There was no significant difference between the systems in directional preponderance (DP) gain or DP time constant. Regarding the VFX test, gain was higher in system [A] than system [B]. Subjects reported less stuffiness and less anxiety with system [B] than system [A], while preferring the system [A] goggles. CONCLUSIONS: A rotation chair system without a darkroom can provide a more comfortable experience for subjects in terms of stuffiness and anxiety, while showing comparable results in SHA and SV tests with a darkroom system.

Treatment of peripheral vestibular dysfunction using photobiomodulation.

Gentamicin, which is still used in modern medicine, is a known vestibular toxic agent, and various degrees of balance problems have been observed after exposure to this pharmacologic agent. Photobiomodulation is a candidate therapy for vertigo due to its ability to reach deep inner ear organs such as the cochlea. Previous reports have suggested that photobiomodulation can improve hearing and cochlea function. However, few studies have examined the effect of photobiomodulation on balance dysfunction. We used a rat model to mimic human vestibulopathy resulting from gentamicin treatment and evaluated the effect of photobiomodulation on vestibular toxicity. Slow harmonic acceleration (SHA) rotating platform testing was used for functional evaluation and both qualitative and quantitative epifluorescence analyses of cupula histopathology were performed. Animals were divided into gentamicin only and gentamicin plus laser treatment groups. Laser treatment was applied to one ear, and function and histopathology were evaluated in both ears. Decreased function was observed in both ears after gentamicin treatment, demonstrated by low gain and no SHA asymmetry. Laser treatment minimized the damage resulting from gentamicin treatment as shown by SHA asymmetry and recovered gain in the treated ear. Histology results reflected the functional results, showing increased hair cell density and epifluorescence intensity in laser-treated cupulae.