Background:Hypometabolism of the posterior cingulate cortex (PCC) is an important diagnostic feature of late-onset, amnestic Alzheimer’s disease (AD) measured with 18F-fluorodeoxyglucose positron emission tomography (FDG-PET). However, it is unclear whether PCC hypometabolism has diagnostic value in young-onset, non-amnestic variants of AD, which exhibit less pathology in the hippocampus and default mode network. Objective:Evaluate the prevalence and diagnostic value of PCC hypometabolism in non-amnestic variants of AD. Methods:We retrospectively identified 60 patients with young-onset, atypical dementia who have undergone a detailed clinical evaluation, FDG-PET, and an amyloid biomarker (amyloid-PET or cerebrospinal fluid analysis). We quantitatively analyzed regional hypometabolism in 70 regions of interest (ROI) using the MIMneuro® software. Results:Based on a cut-off of z-score < –1.5 for significant PCC hypometabolism, the prevalence of PCC hypometabolism in non-amnestic variants of AD was 65% compared to 28% in clinical variants of frontotemporal dementia (FTD). The ROI with the maximal hypometabolism was the dominant middle temporal gyrus in the language variant of AD (mean z score –2.28), middle occipital gyrus in PCA (–3.24), middle temporal gyrus in frontal AD (–2.70), and angular gyrus in corticobasal syndrome due to AD (–2.31). The PCC was not among the 10 most discriminant regions between non-amnestic variants of AD versus clinical variants of FTD. Conclusion:We conclude that PCC hypometabolism is not a discriminant feature to distinguish non-amnestic variants of AD from clinical variants of FTD—and should be interpreted with caution in patients with young-onset, non-amnestic dementia.

中文翻译：

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阿尔茨海默病非遗忘型变异的后扣带皮层代谢减退。

背景：后扣带回皮层 (PCC) 的低代谢是迟发性遗忘性阿尔茨海默病 (AD) 的重要诊断特征，可通过 18F-氟脱氧葡萄糖正电子发射断层扫描 (FDG-PET) 进行测量。然而，尚不清楚 PCC 代谢减退是否对 AD 的年轻发病、非遗忘型变体具有诊断价值，这些变体在海马体和默认模式网络中表现出的病理较少。目的：评估非遗忘型 AD 中 PCC 代谢减退的患病率和诊断价值。方法：我们回顾性确定了 60 名接受详细临床评估、FDG-PET 和淀粉样蛋白生物标志物（淀粉样蛋白 PET 或脑脊液分析）的年轻非典型痴呆患者。我们使用 MIMneuro® 软件定量分析了 70 个感兴趣区域 (ROI) 的区域代谢减退。结果：根据显着 PCC 代谢减退的 z 得分 < –1.5 的临界值，AD 的非遗忘型变体中 PCC 代谢减退的患病率为 65%，而额颞叶痴呆 (FTD) 的临床变体为 28%。最大代谢减退的 ROI 是 AD 语言变体中占主导地位的颞中回（平均 z 得分 –2.28）、PCA 中枕中回 (–3.24)、额叶 AD 中颞中回 (–2.70) 和角回在 AD 引起的皮质基底膜综合征 (–2.31) 中。PCC 不在 AD 的非遗忘性变异与 FTD 的临床变异之间最有区别的 10 个区域之一。结论：我们得出的结论是，PCC 代谢减退不是区分 AD 的非遗忘性变异与 FTD 临床变异的判别特征——并且在年轻发病的患者中应谨慎解释，