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.

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Several electrical stimulation patterns of the auditory nerve have been described for tinnitus relief, but there is no consensus on the most effective stimulation pattern. Therefore, we aim to systematically review the literature on the effect of intra- and extracochlear electrical stimulation patterns as a treatment option for patients with tinnitus. Only studies on intra- and extracochlear electrical stimulation for patients with tinnitus were included if the stimulation used did not concern standardized CI stimulation patterns to primarily rehabilitate hearing loss as intervention. A total of 34 studies met the inclusion criteria, with 10 studies (89 patients) on intracochlear electrical stimulation and 25 studies on extracochlear electrical stimulation (1109 patients). There was a high to medium risk of bias in 22 studies, especially due to lack of a non-exposed group and poor selection of the exposed group. All included studies showed subjective tinnitus improvement during or after electrical stimulation, using different stimulation patterns. Due to methodological limitations and low reporting quality of the included studies, the potential of intra- and extracochlear stimulation has not been fully explored. To draw conclusions on which stimulation patterns should be optimized for tinnitus relief, a deeper understanding of the mechanisms involved in tinnitus suppression is needed.

The aim of this study was to estimate the prevalence and distress of tinnitus pre- and post-cochlear implantation in patients with bilateral severe to profound hearing loss. In this retrospective study, we included patients from a cochlear implant clinic in Perth, Western Australia. Pre- and post-cochlear implantation data from 300 implant recipients were collected on self-reported presence of tinnitus, tinnitus distress using the Tinnitus Reaction Questionnaire (TRQ), hearing-related quality of life using the Abbreviated Profile of Hearing Aid Benefit (APHAB), and consonant-nucleus vowel-consonant (CNC) word recognition test scores. Retrospectively, patients were grouped into those with or without tinnitus, and the grade of tinnitus distress. The potential factors associated with post-implantation changes in the presence of tinnitus and its distress were evaluated. Tinnitus prevalence was 55.8% pre-operatively and 44.3% post-implantation with a median TRQ score respectively of 12.0 (IQR: 1.0–28.0) and 3.5 (IQR: 0.0–16.2) points. Among the 96 patients experiencing tinnitus pre-implantation, 14.6% patients experienced moderate to catastrophic tinnitus distress pre-implantation compared to 6.3% post-implantation. To conclude, the pre- and post-implantation median TRQ score for the cohort population showed that tinnitus was a “slight” handicap. Tinnitus prevalence and its associated tinnitus distress decreased post-implantation. Patients with tinnitus post-implantation were significantly younger and had less severe pre-implantation hearing loss in the non-implanted ear than patients without tinnitus. Further research is needed to understand the factors influencing changes in tinnitus.