Brain Function Research Section, The First Hospital of China Medical University, Shenyang 110001, Liaoning, PR China; Department of Psychiatry, The First Hospital of China Medical University, Shenyang 110001, Liaoning, PR China.
Brain Function Research Section, The First Hospital of China Medical University, Shenyang 110001, Liaoning, PR China; Department of Radiology, The First Hospital of China Medical University, Shenyang 110001, Liaoning, PR China.
Neuroimage Clin. 2022;36:103184. doi: 10.1016/j.nicl.2022.103184. Epub 2022 Sep 7.
Bipolar disorder is a chronic and highly recurrent mental disorder that can be classified as bipolar type I (BD I) and bipolar type II (BD II). BD II is sometimes taken as a milder form of BD I or even doubted as an independent subtype. However, the fact that symptoms and severity differ in patients with BD I and BD II suggests different pathophysiologies and underlying neurobiological mechanisms. In this study, we aimed to explore the shared and unique functional abnormalities between subtypes.
The dynamic amplitude of low-frequency fluctuation (dALFF) was performed to compare 31 patients with BD I, 32 with BD II, and 79 healthy controls (HCs). Global dALFF was calculated using sliding-window analysis. Group differences in dALFF among the 3 groups were compared using analysis of covariance (ANCOVA), with covariates of age, sex, years of education, and mean FD, and Bonferroni correction was applied for post hoc analysis. Pearson and Spearman's correlations were conducted between clusters with significant differences and clinical features in the BD I and BD II groups, after which false error rate (FDR) was used for correction.
We found a significant decrease in dALFF values in BD patients compared with HCs in the following brain regions: the bilateral-side inferior frontal gyrus (including the triangular, orbital, and opercular parts), inferior temporal gyrus, the medial part of the superior frontal gyrus, middle frontal gyrus, anterior cingulum, insula gyrus, lingual gyrus, calcarine gyrus, precuneus gyrus, cuneus gyrus, left-side precentral gyrus, postcentral gyrus, inferior parietal gyrus, superior temporal pole gyrus, middle temporal gyrus, middle occipital gyrus, superior occipital gyrus and right-side fusiform gyrus, parahippocampal gyrus, hippocampus, middle cingulum, orbital part of the medial frontal gyrus and superior frontal gyrus. Unique alterations in BD I were observed in the right-side supramarginal gyrus and postcentral gyrus. In addition, dALFF values in BD II were significantly higher than those in BD I in the right superior temporal gyrus and middle temporal gyrus. The variables of dALFF correlated with clinical characteristics differently according to the subtypes, but no correlations survived after FDR correction.
Our study was cross-sectional. Most of our patients were on medication, and the sample was limited.
Our findings demonstrated neurobiological characteristics of BD subtypes, providing evidence for BD II as an independent existence, which could be the underlying explanation for the specific symptoms and/or severity and point to potential biomarkers for the differential diagnosis of bipolar subtypes.
双相障碍是一种慢性且高度复发的精神障碍，可分为双相 I 型（BD I）和双相 II 型（BD II）。BD II 有时被视为 BD I 的较轻形式，甚至有人怀疑它是一个独立的亚型。然而，BD I 和 BD II 患者的症状和严重程度存在差异，这表明它们具有不同的病理生理学和潜在的神经生物学机制。在这项研究中，我们旨在探索亚型之间共同和独特的功能异常。
采用低频振幅（dALFF）的动态幅度分析方法，比较 31 例 BD I 患者、32 例 BD II 患者和 79 例健康对照者（HCs）。采用滑动窗口分析计算全脑 dALFF。采用协方差分析（ANCOVA）比较 3 组间的 dALFF 组间差异，协变量为年龄、性别、受教育年限和平均 FD，并用 Bonferroni 校正进行事后分析。对 BD I 和 BD II 组中具有显著差异的聚类与临床特征进行 Pearson 和 Spearman 相关性分析，然后用 FDR 进行校正。
与 HCs 相比，BD 患者的 dALFF 值在以下脑区显著降低：双侧额下回（包括三角部、眶部和盖部）、颞下回、额上回内侧部、中额回、前扣带、岛叶、舌回、距状回、楔前叶、楔叶、左中央前回、中央后回、顶下小叶、颞上极回、中颞回、中枕回、上枕回和右梭状回、海马旁回、海马、中扣带回、额内侧回眶部和额上回。BD I 患者还存在右侧缘上回和中央后回的独特改变。此外，BD II 的 dALFF 值在右侧颞上回和中颞回显著高于 BD I。根据亚型的不同，dALFF 值与临床特征的相关性也不同，但在 FDR 校正后没有相关性。
我们的研究是横断面的。我们的大多数患者都在服药，样本量有限。
我们的研究结果表明了双相障碍亚型的神经生物学特征，为 BD II 作为一个独立的存在提供了证据，这可能是特定症状和/或严重程度的潜在解释，并为双相障碍亚型的鉴别诊断提供了潜在的生物标志物。
