Department of Neurosurgery, Tokyo Medical and Dental University, Tokyo, Japan.
Department of Radiology, Juntendo University, Tokyo, Japan.
J Neuroimaging. 2020 Nov;30(6):828-832. doi: 10.1111/jon.12745. Epub 2020 Jun 29.
Transient global amnesia (TGA) is a rare clinical entity with a sudden onset of anterograde amnesia that recovers within 24 hours. The underlying pathophysiology is uncertain. Imaging studies are controversial, but diffusion-weighted images often show small diffusion-restricted lesions in the hippocampus, which may suggest ischemic damage. Thus, we conducted the first clinical study using neurite orientation dispersion and density imaging (NODDI) and arterial spin labeling (ASL) to examine whether the microstructure and perfusion status of the hippocampus are influenced by the presence of diffusion-restricted lesions.
Ten patients with a clinical diagnosis of TGA were evaluated by conventional MRI, NODDI, and ASL. The intracellular volume fraction (ICVF) and orientation dispersion index (ODI) on NODDI and cerebral blood flow (CBF) determined by ASL in the hippocampus were calculated and compared by diffusion-weighted imaging (DWI) positivity. Correlations among ICVF, ODI, and CBF were also analyzed.
Three patients had typical unilateral DWI-positive lesions. No significant differences in any of the three parameters were detected between DWI-positive and DWI-negative hippocampi. A statistically significant correlation was detected between the ODI and CBF (R = .51, P = .021).
The first NODDI and ASL study in patients after TGA demonstrated no obvious microstructural or perfusion abnormalities in the hippocampus with typical DWI-positive lesions, which may indicate that TGA does not cause destructive damage or involve baseline microstructure or perfusion abnormalities in the hippocampus in relation to diffusion-restricted lesions.
短暂性全面性遗忘症（TGA）是一种罕见的临床病症，其特征为突然发作的顺行性遗忘，且在 24 小时内恢复。其潜在的病理生理学机制尚不清楚。影像学研究存在争议，但弥散加权成像（DWI）常显示海马区小的弥散受限病变，这可能提示缺血性损伤。因此，我们进行了首次临床研究，使用神经丝取向分散和密度成像（NODDI）和动脉自旋标记（ASL）来检查海马区弥散受限病变是否会影响微结构和灌注状态。
对 10 例临床诊断为 TGA 的患者进行常规 MRI、NODDI 和 ASL 评估。通过 DWI 阳性计算并比较 NODDI 上的细胞内容积分数（ICVF）和取向弥散指数（ODI），以及 ASL 上的脑血流（CBF）。还分析了 ICVF、ODI 和 CBF 之间的相关性。
3 例患者有典型的单侧 DWI 阳性病变。DWI 阳性和 DWI 阴性海马区的三个参数之间无显著差异。ODI 与 CBF 之间存在统计学显著相关性（R =.51，P =.021）。
TGA 后患者的首次 NODDI 和 ASL 研究表明，典型 DWI 阳性病变的海马区无明显的微结构或灌注异常，这可能表明 TGA 不会导致破坏性损伤，也不会与弥散受限病变相关的海马区基础微结构或灌注异常有关。
