White-matter integrity and hearing acuity decline in healthy subjects: Magnetic resonance tractography

Aim The association between hearing acuity and white-matter (WM) microstructure integrity was evaluated in a normal healthy population with a variety of hearing acuity using an automated tractography technique known as TRACULA (TRActs Constrained by UnderLying Anatomy) in order to investigate whether hearing acuity decline is correlated with brain structural connectivity. Methods Forty healthy controls were recruited to this study, which used a Siemens 3T Trio with a standard eight-channel head coil. Hearing acuity was assessed using pure-tone air conduction audiometry (Amplivox 2160, with Audiocups to eliminate noise and allow accurate pure-tone audiometry). Handedness and anxiety and depression were assessed for all participants in this study using the Edinburgh Handedness Inventory and the Hospital Anxiety and Depression Scale, respectively. Results This study showed a significant reduction in WM volume of the left cingulum angular bundle (CAB; t = 2.32, p = 0.02) in the mild to moderate hearing-loss group (238 +/- 223 mm(2)) compared to the group with normal hearing (105 +/- 121 mm(2)). The WM integrity of the left CAB was found to be significantly different (t = 2.06, p = 0.04) in the mild to moderate hearing-loss group (0.18 +/- 0.06 mm(2)/s) compared to the group with normal hearing (0.22 +/- 0.05 mm(2)/s). The WM integrity of the left anterior thalamic radiation (ATR) was found to be significantly different (t = 2.58, p = 0.014) in the mild to moderate hearing-loss group (0.33 +/- 0.05 mm(2)/s) compared to the group with normal hearing (0.37 +/- 0.03 mm(2)/s). A significant negative correlation was found between age and the WM integrity of the right ATR (r = -0.33, p = 0.038), and between hearing acuity and the WM integrity of the right ATR (r = -0.38, p = 0.013) and left CAB (r = -0.36, p = 0.019). Discussion and conclusion: An important finding in this study is that brain structural connectivity changes in the left hemisphere seem to be associated with age-related hearing loss found mainly in the ATR and CAB tracts.