Valdés Cabrera Diana, Blevins Gregg, Smyth Penelope, Emery Derek, Solar Kevin Grant, Beaulieu Christian
Biomedical Engineering, University of Alberta, Edmonton, Alberta, Canada.
Neurology, University of Alberta, Edmonton, Alberta, Canada.
NMR Biomed. 2023 Apr 18:e4952. doi: 10.1002/nbm.4952.
Hippocampus demyelinating lesions in multiple sclerosis (MS) have been frequently observed in ex vivo histopathological studies; however, they are difficult to image and quantify in vivo. Diffusion tensor imaging (DTI) and T2 mapping could potentially detect such regional in vivo changes if acquired with sufficient spatial resolution. The goal here was to evaluate whether there are focal hippocampal abnormalities in 43 MS patients (35 relapsing-remitting, eight secondary progressive) with and without cognitive impairment (CI) versus 43 controls using high-resolution 1 mm isotropic DTI, as well as complementary methods of T2-weighted and T2 mapping at 3 T. Abnormal hippocampus regions were identified voxel-by-voxel by using mean diffusivity (MD)/T2 thresholds and avoiding voxels attributed to cerebrospinal fluid. When compared with controls, averaged left/right whole hippocampus MD was higher in both MS groups, while lower fractional anisotropy (FA) and volume, and higher T2 relaxometry and T2-weighted signal values, were only significant in CI MS. The hippocampal MD and T2 images/maps were not uniformly affected and focal regions of elevated MD/T2 were evident in MS patients. Both CI and not CI MS groups showed greater proportional areas of the hippocampus with elevated MD, whereas only the CI group showed a greater proportional area of elevated T2 relaxation times or T2-weighted signal. Higher T2 relaxometry and T2-weighted signal values of elevated regions correlated with greater disability and whole hippocampus FA negatively correlated with physical fatigue. High-resolution hippocampus DTI and T2 mapping with less partial volume effects showed whole hippocampus abnormalities with regional elevations of MD/T2 in MS, which could be interpreted as potentially from demyelination, neuron loss, and/or inflammation, and which overall were more extensive in the hippocampus of patients with larger total brain lesion volumes and CI.
在多发性硬化症（MS）中，海马脱髓鞘病变在离体组织病理学研究中经常被观察到；然而，它们在体内难以成像和定量。如果以足够的空间分辨率获取，扩散张量成像（DTI）和T2图谱可能潜在地检测到这种区域体内变化。本研究的目的是使用高分辨率1毫米各向同性DTI以及3T场强下的T2加权和T2图谱等补充方法，评估43例MS患者（35例复发缓解型，8例继发进展型）有无认知障碍（CI）与43例对照相比，海马是否存在局灶性异常。通过使用平均扩散率（MD）/T2阈值逐体素识别异常海马区域，并避免归因于脑脊液的体素。与对照组相比，两个MS组的左右全海马平均MD均较高，而只有CI型MS患者的分数各向异性（FA）和体积较低，T2弛豫测量值和T2加权信号值较高。海马MD和T2图像/图谱并非均匀受影响，MS患者中MD/T2升高的局灶区域明显。CI型和非CI型MS组均显示MD升高的海马比例面积更大，而只有CI组显示T2弛豫时间或T2加权信号升高的比例面积更大。升高区域的较高T2弛豫测量值和T2加权信号值与更大的残疾程度相关，全海马FA与身体疲劳呈负相关。具有较小部分容积效应的高分辨率海马DTI和T2图谱显示MS患者全海马存在异常，MD/T2区域升高，这可能被解释为潜在地源于脱髓鞘、神经元丢失和/或炎症，总体而言，在脑总病变体积较大且有CI的患者海马中更为广泛。
