PP1311 - Tinnitus Residual Inhibition: Exploring Brain, Psychoacoustic, and Psychological Profiles of Responders

Abstract:
Residual inhibition (RI) provides temporary suppression of tinnitus following a specific acoustic stimulation. This study aims to use a published adaptive method that determines inhibition levels (vs. the standard clinical method that identifies only a duration or depth) to assess the prevalence of inhibition and draw profiles of individuals that respond to inhibition. Individual factors (e.g., stress, tinnitus severity and duration) were also examined in relation to RI. Brain activity was recorded to compare responders and non-responders, and to compare conditions in which tinnitus was inhibited or not, controlling for the presence or absence of tinnitus within the same individuals.

Summary:
Rationale
Residual inhibition (RI) is one of the four psychoacoustic parameters used to assess tinnitus in clinic. It is measured by presenting a broadband noise for one minute after which the patient is asked to judge whether tinnitus has decreased or disappeared. The time taken for tinnitus to come back at its usual level, usually seconds, is measured. A key drawback of this procedure is its heavy reliance on the patient’s memory. In our study, we implemented an adaptive method that directly assesses the levels needed to produce sustained inhibition, eliminating the need for memory recall. We compared Responders to Non-Responders and assessed the influence of individual factors such as stress, tinnitus severity and duration, anxiety, and noise exposure on patients. Brain activity was recorded during the task.

Design
Tinnitus frequency and level were assessed using our validated method. The inhibition protocol consisted in presenting noise bursts increasing in levels, either at the tinnitus or at a control (1kHz) frequency, interspersed with silent gaps. Inhibition was considered successful when tinnitus was no longer heard in the silent gaps. Validated questionnaires assessed tinnitus severity (TFI), hyperacusis (HQ), anxiety and depression (HADS), perceived subjective stress (PSS), and coping abilities (BRIEF).

Results
In our sample of 30 individuals with tinnitus (MEAN AGE = 50.1, SD = 15.65), the prevalence of successful inhibition at the tinnitus frequency of was 67% (Responders). The mean inhibition level was 74.7 dB SPL or 42.9 dB SL. When comparing Responders to Non-Responders, they had tinnitus for a shorter time (9 vs. 22 years, respectively), had maladaptive emotional coping abilities (BRIEF EMOTIONAL = 27.6 vs. 24.5), and had marginally lower tinnitus loudness in dB SL (7 vs. 14 dB SL). Brain activity analyses are ongoing.

Conclusions
Successful inhibition was achieved in most tinnitus participants. Responders had a more recent tinnitus, of lower intensity, and higher maladaptive emotional coping strategies, suggesting these factors may influence responsiveness to noise and thus, likeliness to respond to sound therapy, which corroborates with previous studies that have found better outcomes for patients with tinnitus that have not reached a chronic stage.