Exploring the biomechanical responses of human cupula by numerical analysis of temperature experiments

The vestibular receptor of cupula acts an important role in maintaining body balance. However, the cupula buried in the semicircular canals (SCCs) will be destroyed if it is detached from the relevant environment. The mechanical properties of human cupula still remain ambiguous. In this paper, we explored the cupula responses changing with temperature by experiments and numerical simulation of SCCs model. We obtained 3 volunteers’ nystagmus induced by constant angular acceleration when the temperature of volunteers’ SCCs was 36 °C and 37 °C respectively. The slow-phase velocity of 3 volunteers decreased by approximately 3°/s when the temperature of SCCs reduced by 1 °C, which corresponded to the reduction of cupula deformation by 0.3–0.8 μm in the numerical model. Furthermore, we investigated the effects of the variation of endolymphatic properties induced by temperature reduction on cupula deformation through numerical simulation. We found that the decrease of cupula deformation was not caused by the change of endolymphatic properties, but probably by the increase of cupula’s elastic modulus. With the temperature reducing by 1 °C, the cupula’s elastic modulus may increase by 6–20%, suggesting that the stiffness of cupula is enhanced. This exploration of temperature characteristic of human cupula promotes the research of alleviating vestibular diseases.

Exploring the Mechanical Properties of Human Cupula by Numerical Analysis of Temperature Experiments

The vestibular receptor of cupula acts an important role in maintaining body balance. However, the cupula buried in the semicircular canals (SCCs) will be destroyed if it is detached from the relevant environment. The mechanical properties of human cupula still remain ambiguous. In this paper, we explored the cupula’s elastic modulus changing with temperature by experiments and numerical simulation of SCCs model. We obtained 3 volunteers’ nystagmus induced by constant angular acceleration when the temperature of volunteers’ SCCs was 36℃ and 37℃ respectively. The slow-phase velocity of 3 volunteers decreased by approximately 3°/s when the temperature of SCCs reduced by 1℃, which corresponded to the reduction of cupula deformation by 0.3–0.8 µm in the numerical model. Furthermore, we investigated the effects of the variation of endolymphatic properties induced by temperature reduction on cupula deformation through numerical simulation. We found that the decrease of cupula deformation was not caused by the change of endolymphatic properties, but probably by the increase of cupula’s elastic modulus. With the temperature reducing by 1℃, the cupula’s elastic modulus may increase by 6%-20%, suggesting that the stiffness of cupula is enhanced. This exploration of temperature characteristic of human cupula promotes the research of alleviating vestibular diseases.

Influence of vestibular rehabilitation on the recovery of all vestibular receptor organs in patients with unilateral vestibular hypofunction

BACKGROUND: Only a few studies in the literature demonstrate the effect of vestibular rehabilitation (VR) on all vestibular receptor organs. Furthermore, very little evidence of the effect of VR on isolated otolith dysfunction (IOD) is available. OBJECTIVE: The study aimed to investigate the effect of VR on all vestibular receptor organs in patients with different types of unilateral vestibular hypofunction (UVH). METHODS: We enrolled 80 patients with three different types of UVH; combined and isolated loss of semicircular canal and otolith organ function. All patients performed a 12-week customized program of VR and received a full battery of vestibular function tests, before and after the VR. The DHI and SF-36 were performed before, after 6 weeks, and 12 weeks of the VR. RESULTS: Parameters of the caloric test, video head impulse test, ocular and cervical vestibular evoked myogenic potentials were significantly improved after VR. A total of 59 (74%) patients fully recovered, with no significant difference in recovery regarding the type (p = 0.13) and stage of UVH (p = 0.13). All patients reported significantly lower disability and a better quality of life after the VR based on the DHI and SF-36 score. CONCLUSIONS: Vestibular rehabilitation has a positive effect on the recovery of all vestibular receptor organs and it should be used in patients with IOD.

Dynamic Change of VOR and Otolith Function in Intratympanic Gentamicin Treatment for Ménière’s Disease: Case Report and Review of the Literature

Intratympanic gentamicin treatment (IGT) is an evidence-based therapeutic option for recurrent vertigo attacks in Ménière’s disease (MD). Today, in MD it is possible to monitor changes of vestibular receptor function, induced by IGT, with objective test methods such as the video head impulse test (vHIT) and cervical and ocular vestibular evoked myogenic potentials (cVEMP, oVEMP) in a dynamic, time-and frequency-dependent manner. We report on a 65-year-old female patient with recurrent vertigo attacks in a right-sided MD, where receptor function was followed up before and up to 4 weeks after IGT (time dynamic). Quantitative changes of vestibular function (frequency dynamic) were detected with bithermal calorics and vHIT, with air-conducted sound (ACS) cVEMP and bone-conducted vibration (BCV) oVEMP at 500 Hz. The horizontal vestibuloocular reflex (hVOR) gain in vHIT decreased successively until the 4th week with the appearance of catch-up covert and catch-up overt refixation saccades, and side asymmetry increased in caloric testing. Saccular function was extinguished within 4 weeks, whereas utricular function was diminished after 4 weeks. Monitoring vestibular receptor function with objective test methods provides a quantitative insight into the dynamic activity of vestibular function and is therefore applicable in order to adjust IGT regimen at different therapeutic stages.

Regeneration of Vestibular Horizontal Semicircular Canal Afferents in Pigeons

Spontaneous regeneration of vestibular and auditory receptors and their innervating afferents in birds, reptiles, and amphibians are well known. Here, we produced a complete vestibular receptor loss and epithelial denervation using an ototoxic agent (streptomycin), after which we quantitatively characterized the afferent innervation of the horizontal semicircular canals following completed regeneration. We found that calyx, dimorph, and bouton afferents all regenerate in a manner the recapitulates the epithelial topography of normal birds, but over a slow time course. Similar to previous findings in the vestibular otolith maculae, regeneration occurs according to a three-stage temporal sequence. Bouton afferents regenerate during the first month of regeneration, followed by calyceal-bearing afferents in the second and third months. Calyx afferents were the last to regenerate in the final stage of recovery after 3 mo. We also found that regenerated afferents exhibited terminal morphologies that are significantly smaller, less complex, and innervate fewer receptor cells over smaller epithelial areas than those that develop through normative morphogenesis. These structural fiber changes in afferent innervation correlate to alterations in gaze responses during regeneration, although the exact underlying mechanisms responsible for behavioral changes remain unknown. Plasticity in central vestibular neurons processing motion information seem to be required to explain the observed morphologic and response adaptations observed in regenerating vestibular systems.