Secondary Benefits from Tinnitus Retraining Therapy: Clinically Significant Increases in Loudness Discomfort Level and Expansion of the Auditory Dynamic Range

Abstract

In this report, the authors highlight clinically significant improvements in sound tolerance observed over the past decade among patients who were enrolled in tinnitus retraining therapy (TRT) at the University of Maryland Tinnitus and Hyperacusis Center. Pretreatment and TRT follow-up audiometric threshold, loudness discomfort level (LDL), and dynamic-range (DR) data are documented for (1) a group of 68 tinnitus patients who presented with primary complaints of sound intolerance, and (2) a second group of 70 patients who reported only tinnitus (and no sound tolerance problems). TRT-related increases in sound tolerance are (1) due to increases in LDLs and occur independently of changes in audiometric threshold, which were invariant with treatment; (2) statistically significant in tinnitus patients with and without sound tolerance problems, and with and without hearing loss; (3) observed among 81% of the patients with sound tolerance complaints and 44% of the patients who reported primary tinnitus; (4) independent of audiometric frequency over the range 1000 to 8000 Hz; and (5) seemingly independent of TRT treatment duration, which is consistent with recent experimental evidence of a rapid treatment effect (within the first month of TRT). The TRT treatment effects were clinically meaningful, offering new opportunities for expanding the auditory DR and improving sound tolerance in the general hearing-impaired population. The mechanism responsible for the plasticity underlying these treatment effects is uncertain, but appears consistent with a centrally mediated auditory gain control process. Sound tolerance problems were overpredicted among the authors' sample of tinnitus-only patients when existing objective audiometric criteria were used. This finding promoted the development of a new predictive model for sound tolerance problems, which is described in a companion report.