Abstract
The vestibular system plays a crucial role in maintaining postural balance. Unilateral vestibular lesions result in a typical syndrome characterized by postural imbalance, altered locomotor patterns and gaze stabilization, as well as cognitive and neurovegetative disorders. One of the main difficulties encountered in the development of new anti-vertigo drugs is the lack of sensitivity in the evaluation of this syndrome. Qualitative assessments of the vestibular syndrome have been developed, but methods of conducting quantitative evaluations are critically lacking. Recently, assessments with a dynamic weight-bearing device (DWB®, Bioseb) revealed postural alterations in rats subjected to unilateral vestibular neurectomy (UVN). Our team is evaluating a new version of this device capable of quantifying additional parameters of postural and locomotor equilibrium. The objective of this study was to use this device to assess these new posturo-locomotor parameters in a rat model of a vestibular pathology. The biomarkers measured by this device are as follows: the barycenter, the support surface and the weight distribution of the rats when they were moving or stationary. Before UVN, the rats showed a symmetric distribution of their weight along the lateral axis. In the acute phase after UVN on the left side, the rats distributed more weight on the right side than on the left side and then distributed more weight on the left side. These results corroborate those presented in our previous study. The support surface of the rats increased between 1 day and 30 days after UVN, and the barycenter distribution reflected the weight distribution. In addition, our results show smaller changes in the weight distributions when the animals are moving compared with when they are stationary in the acute phase after UVN. This study provides new information on the static and dynamic postural balance patterns observed after unilateral vestibular loss in rats. These data are relevant because they objectively quantify the posturo-locomotor component of vestibular syndrome as well as the compensatory strategies used after vestibular loss. These results may guide the development of rehabilitation protocols for vestibular patients and the validation of pharmacological compounds favoring the restoration of equilibrium.
Highlights
The vestibular system is a sensory-motor system that plays a crucial role in postural control, locomotion, gaze stabilization and space orientation [1] (Figure 1A)
Other behavioral phenotype characteristics of unilateral vestibular injuries were analyzed: the weight distribution on the medial lateral axis, the time spent by the animal leaning on its abdomen, and the number of laps performed during the circling periods
This study analyses the longitudinal effects of a sudden and unilateral suppression of vestibular information on different posturo-locomotor biomarkers: [1] the weight distribution on the lateral axis and the time the animals spend leaning on their abdomen, in static and dynamic condition, [2] the number of turns performed in circling periods, [3] the maximum support surface area and posturographic parameters such as body sway and the amount of energy spent to stabilize (SFA), studied when the animal is static on its four paws
Summary
The vestibular system is a sensory-motor system that plays a crucial role in postural control, locomotion, gaze stabilization and space orientation [1] (Figure 1A) Unilateral damage of this system leads to a vestibular syndrome involving posturolocomotor, oculomotor, perceptual-cognitive and vegetative disorders (Figure 1B), which have a significant impact on patients’ daily lives. The consequences of unilateral vestibular injury are essentially assessed qualitatively by various scales that address several vestibular symptoms (e.g., circling, tumbling, retropulsion, or head-tilting) [4,5,6,7] These different scales describe the overall kinetics of the syndrome, and the disorders are most severe during the first 3 days after injury (a postlesional critical period) and decrease in severity until baseline values are restored (vestibular compensation) [(8) for review]. It is a valuable tool for evaluating the effects of different vestibular therapies (pharmacological and rehabilitative) on the quality and timing of postural functional recovery [14]
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