Current view of neurotransmitter changes underlying tinnitus

Lower glutamate and GABA levels in auditory cortex of tinnitus patients: a 2D-JPRESS MR spectroscopy study

We performed magnetic resonance spectroscopy (MRS) on healthy individuals with tinnitus and no hearing loss (n = 16) vs. a matched control group (n = 17) to further elucidate the role of excitatory and inhibitory neurotransmitters in tinnitus. Two-dimensional J-resolved spectroscopy (2D-JPRESS) was applied to disentangle Glutamate (Glu) from Glutamine and to estimate GABA levels in two bilateral voxels in the primary auditory cortex. Results indicated a lower Glu concentration (large effect) in right auditory cortex and lower GABA concentration (medium effect) in the left auditory cortex of the tinnitus group. Within the tinnitus group, Glu levels positively correlated with tinnitus loudness measures. While the GABA difference between groups is in line with former findings and theories about a dysfunctional auditory inhibition system in tinnitus, the novel finding of reduced Glu levels came as a surprise and is discussed in the context of a putative framework of inhibitory mechanisms related to Glu throughout the auditory pathway. Longitudinal or interventional studies could shed more light on interactions and causality of Glu and GABA in tinnitus neurochemistry.

Multidisciplinary Tinnitus Research: Challenges and Future Directions From the Perspective of Early Stage Researchers

Tinnitus can be a burdensome condition on both individual and societal levels. Many aspects of this condition remain elusive, including its underlying mechanisms, ultimately hindering the development of a cure. Interdisciplinary approaches are required to overcome long-established research challenges. This review summarizes current knowledge in various tinnitus-relevant research fields including tinnitus generating mechanisms, heterogeneity, epidemiology, assessment, and treatment development, in an effort to highlight the main challenges and provide suggestions for future research to overcome them. Four common themes across different areas were identified as future research direction: (1) Further establishment of multicenter and multidisciplinary collaborations; (2) Systematic reviews and syntheses of existing knowledge; (3) Standardization of research methods including tinnitus assessment, data acquisition, and data analysis protocols; (4) The design of studies with large sample sizes and the creation of large tinnitus-specific databases that would allow in-depth exploration of tinnitus heterogeneity.

Temperament and character traits in patients with tinnitus: a prospective case series with comparisons

OBJECTIVE

To describe the personality traits of temperament and character in patients with tinnitus and to identify differences in these traits associated with the severity of tinnitus.

STUDY DESIGN

Case series with comparisons.

SETTING

Tertiary referral centre.

PARTICIPANTS

From January to December 2014, one hundred and thirty-four adult patients with chronic subjective tinnitus completed psychoacoustic measurements of tinnitus and the Temperament and Character Inventory (TCI).

MEASUREMENTS

Personality traits were assessed by the TCI. The TCI assesses seven dimensions of personality traits and four temperaments 'novelty seeking, harm avoidance, reward dependence, persistence', as well as three characters 'self-directedness, cooperativeness, self-transcendence'.

MAIN OUTCOME MEASURES

The values of the TCI parameters in the tinnitus patients were compared with reference data from a non-institutional adult population, and associations between TCI parameter values and tinnitus severity were evaluated.

RESULTS

In terms of temperament, tinnitus patients had higher scores for 'harm avoidance', whereas scores for 'novelty seeking', 'reward dependence' and 'persistence' were significantly lower than the reference. In terms of character, lower 'cooperativeness' and 'self-transcendence' were identified in the subjects with tinnitus. The 'novelty seeking' score was inversely related to tinnitus severity (r = -0.285, P = 0.001), while other temperament and character traits did not show significant correlations.

CONCLUSIONS

There may be a connection between tinnitus and personality traits, especially in the case of 'novelty seeking', which is relatively constant over a lifetime. The TCI questionnaire may be useful in facilitating the application of personality traits to tailored counselling for tinnitus.