Evidence for a Transient State of Auditory Hypersensitivity During Initial Onset of Tinnitus: IDAEP Changes Between Acute and Chronic Tinnitus.

Once persistent for around a month, tinnitus typically persists permanently. This transition from acute to chronic tinnitus is thought to reflect dynamic neurophysiological changes and plasticity within central auditory and non-auditory networks, but empirical evidence has been lacking. We hypothesized that, bottom-up neural mechanisms linked to tinnitus initiation, such as central gain and neural synchrony, are maximal around the time of its initiation, but subsequently return towards baseline as central plastic changes develop. We evaluated part of this hypothesis by measuring central auditory reactivity through the Intensity Dependence of Auditory Evoked Potential (IDAEP), a non-invasive index of higher-order inhibitory processing within the auditory system. A steeper IDAEP slope is associated with heightened sensory reactivity (higher sensitivity to changes in auditory stimuli), indicative of reduced central inhibition, whereas a shallower slope reflects greater inhibitory control. Studying a group with acute tinnitus (onset within past six weeks), with a repeated assessment after six months from onset, we found a significant longitudinal reduction in the IDAEP slope following initial tinnitus onset, and non-significantly higher IDAEP slope in Acute and Chronic tinnitus groups compared to matched controls. These findings support our hypothesis, indicating that IDAEP may serve as an objective marker of auditory reactivity for characterising the time course of certain tinnitus mechanisms.