Does changes in mismatch negativity after tinnitus retraining therapy using tinnitus pitch as deviant stimulus, reflect subjective improvement in tinnitus handicap?

Abstract

Objective: The objective of this research was to study the ability of Mismatch Negativity response parameters to assess the habituation after Tinnitus Retraining Therapy through comparing MMN parameters before and after TRT and comparing MMN in tinnitus patients to non-tinnitus patients, and correlating MMN parameters to subjective measures of tinnitus.Methodology: This research included two groups: a tinnitus group of 30 tinnitus patients who were compared with a control group that consisted of well-matched 10 normal adult subjects. All participants were subjected to full history taking, audiological examination, and MMN test. Tinnitus patients were further assessed for tinnitus severity using the Tinnitus Handicap Inventory (THI), tinnitus analyses including pitch and loudness matching, with the PMF as the deviant stimulus for the MMN test.Results: The MMN latencies were significantly shorter and the MMN amplitudes were significantly greater in the tinnitus group before TRT than the control group. The MMN amplitude after TRT has significantly decreased and the MMN latency has significantly been prolonged in both ears after TRT compared with before TRT. The MMN amplitude improvement matched the subjective improvement measured subjectively by the THI.Conclusion: Tinnitus patients showed abnormality in central auditory processing mechanisms involved in pre-attentive change detection of tinnitus-related neuronal activity. This MMN abnormality showed improvement after habituation using TRT. So, we recommend adding the MMN test in evaluating tinnitus patients objectively before and after TRT for monitoring the treatment progress, together with the usual subjective measures for assessment of the degree of tinnitus severity.