González-Zacarías Clio, Choi Soyoung, Vu Chau, Xu Botian, Shen Jian, Joshi Anand A, Leahy Richard M, Wood John C
Neuroscience Graduate Program, University of Southern California, Los Angeles, CA, United States.
Signal and Image Processing Institute, University of Southern California, Los Angeles, CA, United States.
Front Neurol. 2022 Jul 26;13:894742. doi: 10.3389/fneur.2022.894742. eCollection 2022.
Chronic anemia is commonly observed in patients with hemoglobinopathies, mainly represented by disorders of altered hemoglobin (Hb) structure (sickle cell disease, SCD) and impaired Hb synthesis (e.g. thalassemia syndromes, non-SCD anemia). Both hemoglobinopathies have been associated with white matter (WM) alterations. Novel structural MRI research in our laboratory demonstrated that WM volume was diffusely lower in deep, watershed areas proportional to anemia severity. Furthermore, diffusion tensor imaging analysis has provided evidence that WM microstructure is disrupted proportionally to Hb level and oxygen saturation. SCD patients have been widely studied and demonstrate lower fractional anisotropy (FA) in the corticospinal tract and cerebellum across the internal capsule and corpus callosum. In the present study, we compared 19 SCD and 15 non-SCD anemia patients with a wide range of Hb values allowing the characterization of the effects of chronic anemia in isolation of sickle Hb. We performed a tensor analysis to quantify FA changes in WM connectivity in chronic anemic patients. We calculated the volumetric mean of FA along the pathway of tracks connecting two regions of interest defined by BrainSuite's BCI-DNI atlas. In general, we found lower FA values in anemic patients; indicating the loss of coherence in the main diffusion direction that potentially indicates WM injury. We saw a positive correlation between FA and hemoglobin in these same regions, suggesting that decreased WM microstructural integrity FA is highly driven by chronic hypoxia. The only connection that did not follow this pattern was the connectivity within the left middle-inferior temporal gyrus. Interestingly, more reductions in FA were observed in non-SCD patients (mainly along with intrahemispheric WM bundles and watershed areas) than the SCD patients (mainly interhemispheric).
慢性贫血常见于血红蛋白病患者，主要表现为血红蛋白（Hb）结构改变（镰状细胞病，SCD）和Hb合成受损（如地中海贫血综合征、非SCD贫血）。这两种血红蛋白病均与白质（WM）改变有关。我们实验室的新型结构MRI研究表明，深部分水岭区域的WM体积与贫血严重程度成比例地普遍降低。此外，扩散张量成像分析提供的证据表明，WM微观结构与Hb水平和氧饱和度成比例地受到破坏。SCD患者已得到广泛研究，其在穿过内囊和胼胝体的皮质脊髓束和小脑中表现出较低的各向异性分数（FA）。在本研究中，我们比较了19例SCD患者和15例非SCD贫血患者，这些患者具有广泛的Hb值，从而能够在分离镰状Hb的情况下表征慢性贫血的影响。我们进行了张量分析以量化慢性贫血患者WM连通性中的FA变化。我们计算了沿着由BrainSuite的BCI-DNI图谱定义的两个感兴趣区域之间的轨迹路径的FA体积平均值。总体而言，我们发现贫血患者的FA值较低；这表明主要扩散方向上的连贯性丧失，这可能表明WM损伤。我们在这些相同区域中观察到FA与血红蛋白之间呈正相关，这表明WM微观结构完整性FA的降低高度受慢性缺氧驱动。唯一不遵循这种模式的连接是左中颞下回内的连通性。有趣的是，与SCD患者（主要是半球间）相比，在非SCD患者中观察到更多的FA降低（主要沿着半球内WM束和分水岭区域）。
