Objective assessment of subjective tinnitus through contralateral suppression of otoacoustic emissions by white noise; suggested cut-off points

Systematic review and meta-analysis of late auditory evoked potentials as a candidate biomarker in the assessment of tinnitus

Subjective tinnitus, the perception of sound in the absence of any sound source, is routinely assessed using questionnaires. The subjective nature of these tools hampers objective evaluation of tinnitus presence, severity and treatment effects. Late auditory evoked potentials (LAEPs) might be considered as a potential biomarker for assessing tinnitus complaints. Using a multivariate meta-analytic model including data from twenty-one studies, we determined the LAEP components differing systematically between tinnitus patients and controls. Results from this model indicate that amplitude of the P300 component is lower in tinnitus patients (standardized mean difference (SMD) = -0.83, p < 0.01), while latency of this component is abnormally prolonged in this population (SMD = 0.97, p < 0.01). No other investigated LAEP components were found to differ between tinnitus and non-tinnitus subjects. Additional sensitivity analyses regarding differences in experimental conditions confirmed the robustness of these results. Differences in age and hearing levels between the two experimental groups might have a considerable impact on LAEP outcomes and should be carefully considered in future studies. Although we established consistent differences in the P300 component between tinnitus patients and controls, we could not identify any evidence that this component might covary with tinnitus severity. We conclude that out of several commonly assessed LAEP components, only the P300 can be considered as a potential biomarker for subjective tinnitus, although more research is needed to determine its relationship with subjective tinnitus measures. Future trials investigating experimental tinnitus therapies should consider including P300 measurements in the evaluation of treatment effect.

Evaluation of medial olivocochlear efferent system and hearing loss in patients with primary Sjögren’s syndrome

Background/aim

Autoimmune diseases are a remarkable issue for researchers due to their adverse effects on the auditory system, but for primary Sjögren’s syndrome (pSS) there is little research on the comprehensive audiological findings in literature. The main objective of this study was to investigate the medial olivocochlear efferent functions of subjects with pSS and to examine the audiological findings.

Materials and methods

The study included 36 subjects with pSS and 36 healthy subjects. All the subjects underwent testing including pure tone, speech, and high frequency audiometry; tympanometry and acoustic reflexes; distortion product otoacoustic emissions (DPOAE); and suppression of DPOAE.

Results

The hearing thresholds of the pSS group were higher than those of the control at all frequencies (P < 0.001). Minimal to mild sensorineural hearing loss was observed in 52.77% of all the subjects with pSS. Additionally, all of the subjects had type A curve tympanograms, but the static compliances of the pSS group were lower and the acoustic reflex thresholds were higher than in the control (P < 0.001). In suppression levels of DPOAE, no statistically significant difference was found between the groups (P > 0.05).

Conclusion

The study indicates that because of obtaining normal suppression levels in DPOAE, the medial olivocochlear efferent system is functional in pSS. However, there is a need for more tests, including auditory brainstem response, to evaluate the afferent auditory system in pSS.

Objective assessment of subjective tinnitus through contralateral suppression of otoacoustic emissions by white noise: effects of frequency, gender, tinnitus bilaterality and age

SUMMARY

Accumulating evidence seems to support an association between tinnitus and medial olivocochlear bundle (MOCB) dysfunction. Most studies use patient/control comparisons to support this correlation. The aim of this study was to investigate the hypothesis in a substantially different way and evaluate the roles of gender, age, frequency and tinnitus bilaterality as possible confounding factors. The population consisted of 78 normal hearing patients with chronic tinnitus, 28 normal hearing controls, 19 presbycousic tinnitus patients and 13 presbycousic controls (n = 276 ears). Mean suppression amplitudes of transient evoked otoacoustic emissions (TEOAEs) and distortion product OAEs (DPOAEs) by contralateral white noise (50 dB SPL) were computed. Mean suppression values < 1 dB SPL or < 2 dB SPL were validated as positive test results. Overall suppression (OS) values < 1 dB SPL were qualified as a diagnostic test of moderate positive predictive value for both DPOAEs and TEOAEs, while OS values < 2 dB SPL were found to be of large negative predictive value for DPOAEs and moderate for TEOAEs. Mean suppression values (for all frequencies, OS) are of higher diagnostic value than suppression values corresponding to either lower (1-2 kHz) or higher frequencies (2.8-4 kHz for TEOAEs and 2.8-6 kHz for DPOAEs). After excluding patients with unilateral tinnitus from the analysis, correlations were found to be stronger. Useful correlations were also attributed for all age groups < 61 years. In females, OAE suppression seems to have a stronger positive predictive value, while in males it seems to have a stronger negative predictive value. OAE-based assays of MOCB function as an objective diagnostic tool for subjective tinnitus might deserve further investigation. Tinnitus uni- or bi-laterality is a confounding factor, which probably confirms the observation that defective function of the MOCB usually applies to the contralateral ear as well. Gender is an additional confounding factor, while correlations can be verified for all age groups < 61 years old.