The concept of the right temporal variant of frontotemporal dementia (rtvFTD) is still equivocal. The syndrome accompanying predominant right anterior temporal atrophy has previously been described as memory loss, prosopagnosia, getting lost and behavioural changes. Accurate detection is challenging, as the clinical syndrome might be confused with either behavioural variant FTD (bvFTD) or Alzheimer’s disease. Furthermore, based on neuroimaging features, the syndrome has been considered a right-sided variant of semantic variant primary progressive aphasia (svPPA). Therefore, we aimed to demarcate the clinical and neuropsychological characteristics of rtvFTD versus svPPA, bvFTD and Alzheimer’s disease. Moreover, we aimed to compare its neuroimaging profile against svPPA, which is associated with predominant left anterior temporal atrophy. Of 619 subjects with a clinical diagnosis of frontotemporal dementia or primary progressive aphasia, we included 70 subjects with a negative amyloid status in whom predominant right temporal lobar atrophy was identified based on blinded visual assessment of their initial brain MRI scans. Clinical symptoms were assessed retrospectively and compared with age- and sex-matched patients with svPPA (n = 70), bvFTD (n = 70) and Alzheimer’s disease (n = 70). Prosopagnosia, episodic memory impairment and behavioural changes such as disinhibition, apathy, compulsiveness and loss of empathy were the most common initial symptoms, whereas during the disease course, patients developed language problems such as word-finding difficulties and anomia. Distinctive symptoms of rtvFTD compared to the other groups included depression, somatic complaints, and motor/mental slowness. Aside from right temporal atrophy, the imaging pattern showed volume loss of the right ventral frontal area and the left temporal lobe, which represented a close mirror image of svPPA. Atrophy of the bilateral temporal poles and the fusiform gyrus were associated with prosopagnosia in rtvFTD. Our results highlight that rtvFTD has a unique clinical presentation. Since current diagnostic criteria do not cover specific symptoms of the rtvFTD, we propose a diagnostic tree to be used to define diagnostic criteria and call for an international validation.

中文翻译：

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额颞叶痴呆右侧颞叶变异的临床放射学框架。

额颞叶痴呆（rtvFTD）右侧颞叶变异的概念仍然模棱两可。伴随主要右前颞叶萎缩的综合征以前被描述为记忆力减退、面容失认、迷路和行为改变。准确检测具有挑战性，因为临床综合征可能与行为变异 FTD (bvFTD) 或阿尔茨海默病相混淆。此外，基于神经影像学特征，该综合征被认为是语义变异原发性进行性失语症（svPPA）的右侧变异。因此，我们旨在区分 rtvFTD 与 svPPA、bvFTD 和阿尔茨海默病的临床和神经心理学特征。此外，我们旨在将其神经影像学特征与 svPPA 进行比较，后者与主要的左前颞叶萎缩有关。在临床诊断为额颞叶痴呆或原发性进行性失语症的 619 名受试者中，我们纳入了 70 名淀粉样蛋白阴性的受试者，根据对其初始脑部 MRI 扫描的盲视评估，确定了主要的右颞叶萎缩。回顾性评估临床症状，并与年龄和性别匹配的 svPPA 患者进行比较。n  =  70)、bvFTD ( n  =  70) 和阿尔茨海默病 ( n  = 70)。面容失认、情景记忆障碍和行为改变（如去抑制、冷漠、强迫和失去同理心）是最常见的初始症状，而在疾病过程中，患者会出现语言问题，如找词困难和语焉不详。与其他组相比，rtvFTD 的独特症状包括抑郁、躯体不适和运动/精神迟缓。除右侧颞叶萎缩外，成像模式显示右侧腹额区和左侧颞叶体积减少，这代表了 svPPA 的紧密镜像。双侧颞极和梭状回萎缩与 rtvFTD 面容失认有关。我们的研究结果强调 rtvFTD 具有独特的临床表现。