Unraveling the neurological basis of Tinnitus by studying its initial onset and subsequent chronification

Abstract

Despite tinnitus being too common and present (prevalence: 13%, remission rate: 17.1%), it is still unclear as to why tinnitus is generated and why it persists, thus making it challenging to come up with definitive treatments. For better understanding of tinnitus mechanism, it is warranted to analyse, how the tinnitus transits from its initial onset or acute stages (duration of tinnitus less than 4 weeks) until its chronic stage (duration of tinnitus greater than 6 months). We were motivated to carry out a tinnitus study with an aim to unravel the neurobiological basis of tinnitus by studying its initial onset until its subsequent chronification. We hypothesized that the neural processes such as synchrony and gain (auditory hypersensitivity) linked to tinnitus will be maximal around the onset and reduces over time as a regression to the mean. The study involved individuals with Acute Tinnitus, who were monitored longitudinally for six months post-onset, alongside individuals with Chronic Tinnitus and a Control group matched to the Acute Tinnitus cohort. Our results culminating multiple measures (subjective and objective) of tinnitus reveal that the neural processes linked solely to the tinnitus activity were maximal around the time of onset and reduced over time which is in line with our hypothesis. We further established that measures of generalized auditory sensitivity (gain) do not significantly differ between the groups. Increased dynamic range adaptation, were observed in the Acute Tinnitus group, but not in the Chronic Tinnitus or Control groups thus indicating that tinnitus is an outcome of excess auditory hyperactivity as an invariance (mitigator) to central gain through properties of increased dynamic range adaptation that tends to persist through modes of sustained attentional networks. This would explain why tinnitus generates and persists as it seeks to modulate excessive hypersensitivity within the auditory system.