GIGA Research, CRC Human Imaging, University of Liege, Liege, Belgium.
Cortex. 2024 Oct;179:50-61. doi: 10.1016/j.cortex.2024.07.004. Epub 2024 Aug 3.
18F-fluoro-deoxy-glucose positron emission tomography (FDG-PET) is a useful paraclinical exam for the diagnosis of Alzheimer's disease (AD). In this narrative review, we report seminal studies in clinically probable AD that have shown the importance of posterior brain metabolic decrease and the paradoxical variability of the hippocampal metabolism. The FDG-PET pattern was a sensitive indicator of AD in pathologically confirmed cases and it was used for differential diagnosis of dementia conditions. In prodromal AD, the AD FDG-PET pattern was observed in converters and predicted conversion. Automated data analysis techniques provided variable accuracy according to the reported indices and machine learning methods showed variable reliability of results. FDG-PET could confirm AD clinical heterogeneity and image data driven analyses identified hypometabolic subtypes with variable involvement of the hippocampus, reminiscent if the paradoxical FDG uptake. In studies dedicated to clinical and metabolic correlations, episodic memory was related to metabolism in the default mode network (and Papez's circuit) in prodromal and mild AD stages, and specific cognitive processes were associated to precisely distributed brain metabolism. Cerebral metabolic correlates of anosognosia could also be related to current neuropsychological models. AD FDG-PET pattern was reported in preclinical AD stages and related to cognition or to conversion to mild cognitive impairment (MCI). Using other biomarkers, the AD FDG-PET pattern was confirmed in AD participants with positive PET-amyloid. Intriguing observations reported increased metabolism related to brain amyloid and/or tau deposition. Preserved glucose metabolism sometimes appear as a compensation, but it was frequently detrimental and the nature of such a preservation of glucose metabolism remains an open question. Limbic metabolic involvement was frequently related to non-AD biomarkers profile and clinical stability, and it was reported in non-AD pathologies, such as the limbic predominant age-related encephalopathy (LATE). FDG-PET abnormalities observed in the absence of classical AD proteinopathies can be useful to search for pathological mechanisms and differential diagnosis of AD.
18F-氟代脱氧葡萄糖正电子发射断层扫描（FDG-PET）是诊断阿尔茨海默病（AD）的一种有用的临床辅助检查。在本综述中，我们报告了在临床上可能的 AD 中具有重要意义的开创性研究，这些研究表明了大脑后部代谢降低和海马代谢反常变化的重要性。FDG-PET 模式是病理性确诊 AD 的敏感指标，并用于痴呆症的鉴别诊断。在前驱期 AD 中，AD 的 FDG-PET 模式在转化者中观察到，并可预测转化。根据报道的指标，自动化数据分析技术提供了不同的准确性，而机器学习方法显示了结果的可靠性存在差异。FDG-PET 可以确认 AD 的临床异质性，图像数据驱动分析确定了代谢低下的亚型，海马的参与程度不同，类似于反常的 FDG 摄取。在专门针对临床和代谢相关性的研究中，在前驱期和轻度 AD 阶段，情景记忆与默认模式网络（和帕佩兹环路）的代谢有关，特定的认知过程与精确分布的大脑代谢有关。失认症的大脑代谢相关性也可能与当前的神经心理学模型有关。在临床前 AD 阶段也报告了 AD 的 FDG-PET 模式，与认知或转化为轻度认知障碍（MCI）有关。使用其他生物标志物，在 AD 参与者中也证实了 AD 的 FDG-PET 模式与 PET-淀粉样蛋白阳性相关。有趣的观察结果表明，与大脑淀粉样蛋白和/或 tau 沉积相关的代谢增加。葡萄糖代谢的保留有时似乎是一种代偿，但它经常是有害的，这种葡萄糖代谢的保留的性质仍然是一个悬而未决的问题。边缘代谢的参与通常与非 AD 生物标志物谱和临床稳定性有关，并在非 AD 病理学中报告，如边缘优势型与年龄相关的脑病（LATE）。在没有典型 AD 蛋白病的情况下观察到的 FDG-PET 异常有助于寻找 AD 的病理机制和鉴别诊断。
