Vestibular end-organ impairment in an animal model of type 2 diabetes mellitus

Objectives/Hypothesis: To define and assess the functional impairment of th e vestibular part of the inner ear in a diabetic state, using a direct and objective test for evaluating the vestibular end-organ and an animal model for diet-induced type 2 diabetes mellitus. Study Design: Prospective contro lled animal study. Methods: Two groups of sand rats (Psammomys obesus) were maintained on two different diets. The experimental group received a speci ally designed high-energy diet known to induce a diabetic state, and the co ntrol group a low-energy diet maintaining these animals in a normal metabol ic state. After 1 month of documented hyperglycemia in the experimental gro up, recordings of vestibular evoked potentials (VsEPs) and recordings of au ditory brainstem response (ABR) were conducted in all animals. The latency and the amplitude of the first wave of both responses, shown to reflect end -organ activity, were compared between the two groups. Results: The mean la tency of the first wave of the VsEPs was significantly (P = .002) prolonged and the amplitude was significantly (P = .005) decreased in the diabetic g roup in comparison to the control group. The latency of the first wave of A BR was significantly (P = .02) prolonged, the amplitude was not significant ly decreased, and threshold was significantly elevated (P = .01) in the dia betic group. Conclusion: For the first time, using an objective assessment test, functional impairment of the vestibular part of the inner ear has bee n demonstrated in the diabetic metabolic state. Despite this being an anima l study, these findings would seem to indicate that the vestibular-end-orga n should be added to the long list of organs and tissues adversely affected by diabetes.