Many patients who meet core/root criteria for Primary Progressive Aphasia (PPA) are not classifiable as a recognized variant and are often excluded from neuroimaging studies. Here, we detail neurological, neuropsychological, speech and language assessments, and anatomic and molecular neuroimaging (MRI, PiB-PET, and FDG-PET) for fifteen (8 female) clinically unclassifiable PPA patients. Median age of onset was 64 years old with median 3 years disease duration at exam. Three patients were amyloid positive on PiB-PET. 14/15 patients had abnormal FDG-PETs with left predominant hypometabolism, affecting frontal, temporal, parietal, and even occipital lobes. Patients had mild to severe clinical presentations. Visualization of the FDG-PETs principal component analysis revealed patterns of hypometabolism similar to those seen in the PPA variants and suggests the brain regions affected in unclassifiable PPA patients are no different from those who are more easily classifiable. These findings may inform future modifications to the diagnostic criteria to improve diagnostic classification.

中文翻译：

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临床无法分类的原发性进行性失语症的临床和神经影像学特征

许多符合原发性进行性失语症 (PPA) 核心/根本标准的患者不能归类为公认的变异，并且通常被排除在神经影像学研究之外。在这里，我们详细介绍了 15 名（8 名女性）临床无法分类的 PPA 患者的神经学、神经心理学、言语和语言评估以及解剖和分子神经影像（MRI、PiB-PET 和 FDG-PET）。中位发病年龄为 64 岁，检查时中位病程为 3 年。三名患者的 PiB-PET 呈淀粉样蛋白阳性。14/15 的患者 FDG-PET 异常，左侧代谢减退为主，影响额叶、颞叶、顶叶，甚至枕叶。患者有轻度至重度的临床表现。FDG-PET 主成分分析的可视化揭示了与 PPA 变体中相似的代谢低下模式，并表明无法分类的 PPA 患者受影响的大脑区域与那些更容易分类的患者没有什么不同。这些发现可能会为未来诊断标准的修改提供信息，以改进诊断分类。