Primary progressive aphasia (PPA) diagnostic criteria underestimate the complex presentation of semantic (sv) and logopenic (lv) variants, in which symptoms partially overlap, and mixed clinical presentation (mixed-PPA) and heterogenous profile (lvPPA +) are frequent. Conceptualization of similarities and differences of these clinical conditions is still scarce. Lexical, semantic, phonological, and working memory errors from nine language tasks of sixty-seven PPA were analyzed using Profile Analysis based on Multidimensional Scaling, which allowed us to create a distributed representation of patients’ linguistic performance in a shared space. Patients had been studied with [18F] FDG-PET. Correlations were performed between metabolic and behavioral data. Patients’ profiles were distributed across a continuum. All PPA, but two, presented a lexical retrieval impairment, in terms of reduced production of verbs and nouns. svPPA patients occupied a fairly clumped space along the continuum, showing a preponderant semantic deficit, which correlated to fusiform gyrus hypometabolism, while only few presented working memory deficits. Adjacently, lvPPA + presented a semantic impairment combined with phonological deficits, which correlated with metabolism in the anterior fusiform gyrus and posterior middle temporal gyrus. Starting from the shared phonological deficit side, a large portion of the space was occupied by all lvPPA, showing a combination of phonological, lexical, and working memory deficits, with the latter correlating with posterior temporo-parietal hypometabolism. Mixed PPA did not show unique profile, distributing across the space. Different clinical PPA entities exist but overlaps are frequent. Identifying shared and unique clinical markers is critical for research and clinical practice. Further research is needed to identify the role of genetic and pathological factors in such distribution, including also higher sample size of less represented groups.

中文翻译：

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原发性进行性失语症的语词减少和语义变异的语言特征连续体的异质性和重叠：基于多维尺度研究的特征分析

原发性进行性失语 (PPA) 诊断标准低估了语义 (sv) 和语词减少 (lv) 变异的复杂表现，其中症状部分重叠，并且混合临床表现 (混合 PPA) 和异质特征 (lvPPA +) 很常见。这些临床状况的相似点和差异的概念仍然很少。使用基于多维尺度的轮廓分析对 67 个 PPA 的 9 个语言任务中的词汇、语义、语音和工作记忆错误进行了分析，这使我们能够在共享空间中创建患者语言表现的分布式表示。患者已接受[18F] FDG-PET 研究。在代谢和行为数据之间进行相关性分析。患者的概况分布在一个连续体中。除了两个之外，所有 PPA 都存在词汇检索障碍，即动词和名词产生量减少。svPPA 患者沿着连续体占据相当集中的空间，表现出明显的语义缺陷，这与梭状回代谢低下相关，而只有少数患者出现工作记忆缺陷。此外，lvPPA + 呈现语义障碍和语音缺陷，这与梭状前回和颞中回后部的代谢相关。从共同的语音缺陷一侧开始，大部分空间被所有 lvPPA 占据，显示出语音、词汇和工作记忆缺陷的组合，后者与后颞顶叶代谢低下相关。混合 PPA 没有表现出独特的轮廓，分布在整个空间中。存在不同的临床 PPA 实体，但重叠很常见。识别共享和独特的临床标志物对于研究和临床实践至关重要。需要进一步的研究来确定遗传和病理因素在这种分布中的作用，包括代表性较少的群体的更大样本量。