Etiology and Pathophysiology of Tinnitus - A Systematic Review.

Prevalence of tinnitus range from 7.1% to 14.6% (National Center for Health Statistics, 2016), but the mechanisms responsible for the development of this abnormal sensory state remain poorly understood. To determine the evidence for different etiologies and pathophysiology of tinnitus identified by clinical diagnostic tests in the adult population. Systematic literature review. Review of data base using PRISMA guidelines: Google Scholar, Medline, Springer Link, Pubmed. In addition, manual reference search of identified papers. Randomized controlled trials, case control study, prospective cohort studies, and retrospective reviews of consecutive patients in which clear data were reported with respect to etiology and pathophysiology of tinnitus. Sixty seven articles met the inclusion criteria. The papers searched recent studies from 2004 to 2018 for different etiologies such as noise exposure, age, ototoxic drugs, hearing loss among patients with tinnitus. Multiple pathophysiology were identified, including inner ear pathology, auditory nerve synchronisation, central nervous system anomalies and limbic and autonomous nervous system problems. The group of papers evaluated tinnitus patients with specific diagnostic tests such as pure tone audiometry, Immitance audiometry, otoacoustic emission, Auditory brainstem response and diagnostic imaging of fMRI, MRI and PET study. The results indicate a high level of heterogeneity between the studies for all the assessed areas. These results support the need for greater stratification of the tinnitus population and the importance of a standardized Puretone audiometry with extended high frequency, OAE, ABR and diagnostic imaging (fMRI, MRI & PET) method to make comparisons between studies possible. Diagnostic imaging is an important useful method for identification of intracranial pathology that can present with tinnitus as a primary symptom. Establishment of a direct causal link between tinnitus and these etiologies and pathophysiology remains elusive.