Increased basal ganglia volume in older adults with tinnitus

Abstract

Tinnitus is the perception of sounds without external stimuli, affecting 10%-15% of the general population and up to 25% of individuals over 70 years of age. While traditionally viewed as an auditory phenomenon, growing evidence highlights the role of the central nervous system in its pathophysiology. One of the proposed mechanisms, the "gating hypothesis" of tinnitus, suggests an alteration in the modulation of sensory activity by the frontostriatal network. Although structural changes in frontal areas support this idea, gray matter differences in subcortical regions-such as the auditory pathway and basal ganglia-remain poorly understood. Here, we examined subcortical structures and auditory function in older adults with mild presbycusis from the ANDES cohort, including 51 tinnitus patients and 40 age-matched controls. We analyzed brain volume via structural magnetic resonance imaging and subcortical auditory functionality via auditory brainstem responses (ABRs). We found non-significant differences in age, hearing loss, cognitive impairment, and ABR amplitudes between the groups. Notably, tinnitus patients presented a significant increase in the volume of basal ganglia structures (striatum and pallidum) but not in auditory areas. These findings reinforce the role of the basal ganglia in age-related tinnitus pathophysiology.

Keywords: Aging; Basal ganglia; MRI; Presbycusis; Sensory gating; Tinnitus.

Fig. 1

Educational level and audiological assessments. a) There were significant differences between groups in terms of years of education, being lower in tinnitus. b) The mean age and hearing levels of the tinnitus and non-tinnitus groups were similar. Significant correlations between PTA and age were found for both groups (T: Spearman rho = 0.48, p = 0.0003; NT: Spearman rho = 0.38, p = 0.013). c) The Hearing Handicap Inventory (HHIE-S) did not differ between the groups in terms of quality of life or emotional well-being with respect to hearing difficulties. d) Significant differences between groups were found in the loudness discomfort level (LDL), as the tinnitus group had a greater number of audiogram frequencies with detectable LDL, denoting a higher index for hyperacusis (T: 3.76 ± 4.1; NT: 1.92 ± 3.22, p = 0.02). * = statistically significant p < 0.05., ns = non-significant, p ≥ 0.05.

Fig. 2

Functional evaluation of the central auditory pathway using suprathreshold ABR in the groups with and without tinnitus. a) The wave V/I ratio comparison revealed no difference between healthy controls and tinnitus patients. b) Non-significant difference in auditory-nerve (Wave I) amplitude. (c) Non-significant difference in wave V amplitude. ns = non-significant p ≥ 0.05.

Fig. 3

Volumetric MRI comparisons of the central auditory pathway in the groups with and without tinnitus. There were no significant differences between the groups in any of the structures measured. ns = non-significant p ≥ 0.05.

Fig. 4

Basal ganglia volume comparisons. Volumetric comparisons of nonauditory subcortical structures revealed that tinnitus patients have larger pallidum (a), putamen (b), caudate (c), and nucleus accumbens (d) structures. *p < 0.05, **p < 0.01, ***p < 0.001.

Fig. 5

Anatomical reference for the basal ganglia structures analyzed, along with their corresponding t-values calculated for the statistical comparisons.

Fig. 6

Interactions and effect of group (tinnitus vs. non-tinnitus) on striatum volume, with age (a) and PTA (b) as predictors. The striatum volume is the sum of the putamen, caudate, and accumbens volume structures.