Lee Sang-Yeon, Kim Heejung, Lee Jun Young, Kim Ju Hye, Lee Dong Young, Mook-Jung Inhee, Kim Young Ho, Kim Yu Kyeong
Department of Otorhinolaryngology, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seoul, South Korea.
Department of Nuclear Medicine, Seoul National University Boramae Medical Center, Seoul National University College of Medicine, Seoul, South Korea.
Front Aging Neurosci. 2020 Nov 19;12:594282. doi: 10.3389/fnagi.2020.594282. eCollection 2020.
Tinnitus is a conscious auditory perception in the absence of an external stimulus. Despite previous reports of a recognized association between tinnitus and cognitive deficits, the effects of tinnitus on functional and structural brain changes associated with cognitive deficits remain unknown. We aimed to investigate the changes in glucose metabolism and gray matter (GM) volume in subjects diagnosed with mild cognitive impairment (MCI) depending on tinnitus. Twenty-three subjects were subclassified into MCI with the chronic tinnitus (MCI_T) and MCI without tinnitus (MCI_NT) groups. Encouraged by the identification of neural substrates associated with tinnitus and cognitive deficits, we correlated the extent of tinnitus severity with the changes in glucose metabolism and GM volume and conducted a glucose metabolic connectivity study. Compared to the MCI_NT group, the MCI_T group showed significantly lower metabolism in the right superior temporal pole and left fusiform gyrus. Additionally, the GM volume in the right insula was markedly lower in the MCI_T group compared to the MCI_NT group. Moreover, correlation analyses in metabolism or GM volumes revealed specific brain regions associated with the cognitive decline with increasing tinnitus severity. Metabolic connectivity analysis revealed that MCI_NT had markedly strengthened intra-hemispheric connectivity in the frontal, parietal, and occipital regions than did MCI_T. Furthermore, MCI_NT showed a strong negative association between the parietal and temporal and parietal and limbic regions, but the association was not observed in MCI_T. These findings indicate that tinnitus may cause metabolic and structural changes in the brain and alters complex inter- or intra-hemispheric networks in MCI. Considering the impact of MCI on accelerating dementia, these results provide a valuable basis on which yet-to-be-identified neurodegenerative markers of tinnitus can be refined.
耳鸣是在没有外部刺激时的一种有意识的听觉感知。尽管先前有报道称耳鸣与认知缺陷之间存在公认的关联，但耳鸣对与认知缺陷相关的大脑功能和结构变化的影响仍不清楚。我们旨在研究根据耳鸣情况，被诊断为轻度认知障碍（MCI）的受试者的葡萄糖代谢和灰质（GM）体积的变化。23名受试者被分为慢性耳鸣的MCI（MCI_T）组和无耳鸣的MCI（MCI_NT）组。受与耳鸣和认知缺陷相关的神经基质的识别鼓舞，我们将耳鸣严重程度与葡萄糖代谢和GM体积的变化进行关联，并进行了葡萄糖代谢连通性研究。与MCI_NT组相比，MCI_T组在右侧颞上极和左侧梭状回的代谢明显较低。此外，与MCI_NT组相比，MCI_T组右侧岛叶的GM体积明显更低。此外，对代谢或GM体积的相关分析揭示了随着耳鸣严重程度增加与认知衰退相关的特定脑区。代谢连通性分析显示，与MCI_T组相比，MCI_NT组在额叶、顶叶和枕叶区域的半球内连通性明显增强。此外，MCI_NT组在顶叶与颞叶以及顶叶与边缘叶区域之间显示出强烈的负相关，但在MCI_T组中未观察到这种相关性。这些发现表明，耳鸣可能会导致大脑中的代谢和结构变化，并改变MCI中复杂的半球间或半球内网络。考虑到MCI对加速痴呆的影响，这些结果为尚未确定的耳鸣神经退行性标志物的完善提供了有价值的基础。
