Asymmetric hearing loss is associated with altered white matter mesostructure and cortical measures in temporal and occipital regions

Purpose To explore the differences in gray and white matter integrity between patients with asymmetric hearing loss (AHL) and normal-hearing controls (NH) using structural MRI and diffusion tensor imaging (DTI).

Methods Nine right-handed adults with left AHL and 12 matched NH controls received 3.0 T-MRI of the brain. CAT-12 derived tissue probability values of gray matter (GM) in the temporal, occipital and postcentral cortex were measured. Microstructure was assessed with DTI-derived fractional anisotropy (FA) in temporal, occipital and postcentral white matter regions. For group comparison, the asymmetry index (AI) for FA/GM was calculated: ipsi- minus contralateral divided by their mean. Negative AI reflect higher values in the ipsilateral region and positive AI reflect higher values in the contralateral region.

Results Significantly higher FA-AI was found in the middle temporal region in AHL than NH (mean -0.03 vs. -0.07; p=0.02). The GM-AI of the inferior temporal cortex in AHL was significantly increased compared to NH (mean 0.07 vs. 0.04, p=0.02). A trend level higher GM-AI of the middle temporal cortex was seen in AHL (mean 0.07 vs. 0.05, p=0.08). In the superior occipital cortex, the GM-AI was significantly higher in AHL than NH (mean 0.0006 vs. -0.07; p=0.02).

Conclusion Our results suggest that left AHL results in a reduction of FA-AI of the right middle temporal region, which indicates an increased connectivity contralateral to the more hearing-impaired ear. This might be due to cross-modal plasticity as we observed a loss of asymmetry in the superior occipital lobe in AHL, whereas in both NH and AHL the right inferior temporal cortex GM values were higher, but more pronounced in AHL. This could reflect the increased connectivity of the temporal region.

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Publication History

Article published online:
12 May 2023