Quantitative analysis of white matter brain changes in tinnitus patients with normal hearing: a case-controlled study with diffusion tensor imaging

Abstract

Background This research aimed at assessing the white matter microstructural (WM) brain changes in tinnitus patients with bilateral normal peripheral hearing using diffuse tensor imaging to test whether, tinnitus alone without hearing loss can cause WM brain changes or not. Patients and materials Twenty-eight patients were enrolled in this research, 14 patients with bilateral tinnitus without hearing loss (audiometrically proven) and 14 normal hearing controls. All subjects underwent a full basic audiological evaluation, tinnitus matching, and were asked to fill the Tinnitus Handicap Inventory (THI) questionnaire. They underwent diffusion tensor brain imaging, mean diffusivity (MD) and fractional anisotropy (FA) values were measured at special parts of central auditory pathway, and parts of limbic system. A comparison between study and control groups was held as regards MD and FA at different brain sites using an independent sample Student t-test or Mann–Whitney U test. Furthermore, the relationship between THI scores and the MD/FA measures was examined by correlation tests. Results As regards FA values, some regions as [lateral lemniscus (LL), inferior colliculus (IC), frontal arcuate fasciculi (AF) and parahippocampus] showed statistically significant decreased FA values in the tinnitus group compared to Normal Hearing (NH) group (p < 0.05). As regards MD values, tinnitus patients showed significantly higher MD values at (auditory cortex, amygdala, and AF) compared to control group (p < 0.05). As regards correlations, THI scores showed statistically significant positive correlation with MD values measured at Rt Amygdala (r = 0.55, p = 0.04). Conclusions The central auditory pathway affection is proved in tinnitus patients with normal hearing (as least as evidenced by conventional audiological examinations) and the auditory-limbic association is proved so far. The involvement of IC confirms the subcortical auditory centres involvement in the generation of the tinnitus. Auditory associations are also significantly impacted by the effect of tinnitus.