The Importance of Aging in Gray Matter Changes Within Tinnitus Patients Shown in Cortical Thickness, Surface Area and Volume

Aging and sensorineural hearing loss are known to be involved in the development of chronic tinnitus. This study explores the structural changes of gray matter using surface base methods and focuses more specifically on changes in cortical thickness in 127 tinnitus patients. The linear relationships between cortical thickness and behavioral measures including aging, tinnitus loudness, tinnitus duration, tinnitus distress, and hearing loss were analyzed. Three dimensional T1-weighted MR images were acquired and cortical gray matter volumes were segmented using FreeSurfer on Talairach space. The results showed that cortical thickness and volume are negatively correlated to age in widespread regions of frontal cortices, and positively to bilateral entorhinal cortex and left rostral anterior cingulate cortex. The cortical thickness changes related to hearing loss overlap with those related to normal aging. The gray matter volumes of bilateral amygdalae, hippocampi, nuclei accumbens, and thalami are all significantly negatively correlated to age. Tinnitus-related distress level and subjective loudness were negatively correlated only to the thalamic volume. The results suggest that the primary factor of long-term structural changes in chronic tinnitus patients is age and age related hearing loss, rather than hearing loss per se. Tinnitus related factors such as subjective tinnitus loudness, tinnitus duration, and the level of chronic tinnitus related distress were not correlated to important morphometric changes in this study.