Vestibular functional assessment using the caloric test in mice with arsanilic acid-induced vestibular dysfunction

The vestibular system contributes to postural control, eye movements, spatial perception, and autonomic regulation. Its dysfunction causes vertigo, nausea, postural instability, which gradually improve via central plasticity known as vestibular compensation. Experimental vestibular compensation studies commonly use unilateral vestibular neurectomy or chemical/labyrinthectomy models, with vestibular function assessed by vestibulo-ocular reflex (VOR) analysis, vestibular evoked myogenic potentials, and vestibular sensory evoked potentials. However, these methods require specialized equipment. In contrast, the caloric test, widely used clinically, offers a simple means of evaluating lateral semicircular canal function, yet its use in animal studies remains limited. In this study, a chemical vestibular lesion was induced using arsanilic acid, and vestibular function was evaluated with the caloric test and VOR analysis. In normal mice, cold-water stimulation elicited nystagmus whose direction reversed with head position. In the arsanilic acid-induced vestibular dysfunction mice, day 3-lesioned side stimulation showed no significant difference in maximum slow-phase velocity (MSPV) compared with normal mice. In contrast, MSPV was reduced on the unaffected side compared with the affected side and controls. Conversely, VOR analysis demonstrated a significant gain increase in the arsanilic acid-induced vestibular dysfunction mice. Thus, the caloric test may provide complementary information on unaffected-side functional modulation during early vestibular compensation that is not captured by VOR analysis alone. The caloric test effectively assessed normal and impaired vestibular function and, with VOR analysis, may clarify vestibular compensation mechanisms. Given its simplicity, the caloric test is a promising complementary method for assessing vestibular function in mouse models and may aid studies of vestibular compensation.