Balance dysfunction resulting from acute inner ear energy failure is caused primarily by vestibular hair cell damage

Assessment of the Progression of Vertical Semicircular Canal Dysfunction and Increased Vestibular Endolymphatic Hydrops in Patients With Early-Stage Ménière Disease

Importance

Vertical semicircular canals and endolymphatic hydrops play important roles in the pathophysiological mechanisms of Ménière disease. However, their characteristics and associations with disease progression during medical treatment have not been determined.

Objective

To examine the function of both the horizontal and vertical semicircular canals in patients with Ménière disease and to evaluate the change in endolymphatic hydrops volume during medical treatment, including treatment with diuretic therapy, over a 2-year period.

Design, Setting, and Participants

This prospective longitudinal observational cohort study included 55 patients with definite unilateral Ménière disease and was performed in a tertiary care hospital in Japan. Participants were enrolled between April 1, 2017, and January 31, 2018, and those with vestibular migraine were excluded. All participants received education regarding diet and lifestyle modifications and treatment with betahistine mesylate (36 mg daily) and/or an osmotic diuretic (42-63 mg daily). Patients were followed up for vertigo and hearing evaluations at least once per month for more than 12 months and were instructed to record episodes of vertigo in a self-check diary. Audiometry was performed monthly, video head impulse testing and caloric testing were performed every 4 months, and magnetic resonance imaging was conducted annually. Data were analyzed from May 15, 2017, to January 31, 2020.

Main Outcomes and Measures

Neurootological testing to evaluate vestibuloocular reflex gain over time, magnetic resonance imaging to evaluate the change in endolymphatic hydrops volume over time, and monthly vertigo and hearing evaluations for more than 12 months.

Results

Among 55 participants with definite Ménière disease, 32 patients (58.2%) were female, and the mean (SD) age was 59.0 (15.1) years. The median disease duration was 2 years (interquartile range, 0-4 years), with 43 patients (78.2%) having an early stage (ie, disease duration ≤4 years) of Ménière disease. Over the 2-year study period, the vestibuloocular reflex gain decreased from 0.76 to 0.56 in the superior semicircular canals, for a difference of 0.20 (95% CI, 0.14-0.26) and from 0.68 to 0.50 in the posterior semicircular canals, for a difference of 0.18 (95% CI, 0.14-0.22). The maximum slow-phase velocity and vestibuloocular reflex gain in the horizontal semicircular canals were maintained. The volume ratio of vestibular endolymphatic hydrops increased from 19.7% to 23.3%, for a difference of 3.6% (95% CI, 1.4%-5.8%). The frequency of vertiginous episodes decreased, and the hearing level over the study period worsened from 40.9 dB to 44.5 dB, for a difference of 3.5 dB (95% CI, 0.7-6.4 dB).

Conclusions and Relevance

In this study, during a 2-year period of medical treatment among patients with Ménière disease, vestibuloocular reflex gain decreased in the vertical semicircular canals but was maintained in the horizontal semicircular canals; the endolymphatic hydrops volume ratio increased, and the frequency of vertiginous episodes decreased. These findings describe the pathological progression of chronic Ménière disease and expand the understanding of its pathophysiological characteristics during the early stage of disease.

Expression and function of Sox21 during mouse cochlea development

The development of the inner ear is an orchestrated process of morphogenesis with spatiotemporally controlled generations of individual cell types. Recent studies have revealed that the Sox gene family, a family of evolutionarily conserved HMG-type transcriptional factors, is differentially expressed in each cell type of the mammalian inner ear and plays critical roles in cell-fate determination during development. In this study, we examined the expression pattern of Sox21 in the developing and adult murine cochlea. Sox21 was expressed throughout the sensory epithelium in the early otocyst stage but became restricted to supporting cells during adulthood. Interestingly, the expression in adults was restricted to the inner phalangeal, inner border, and Deiters' cells: all of these cells are in direct contact with hair cells. Evaluations of the auditory brainstem-response revealed that Sox21(-/-) mice suffered mild hearing impairments, with an increase in hair cells that miss their appropriate planar cell polarity. Taken together with the previously reported critical roles of SoxB1 families in the morphogenesis of inner ear sensory and neuronal cells, our results suggest that Sox21, a counteracting partner of the SoxB1 family, controls fine-tuned cell fate decisions. Also, the characteristic expression pattern may be useful for labelling a particular subset of supporting cells.