The behavioural variant of frontotemporal dementia (bvFTD) is a frequent cause of early-onset dementia. The diagnosis of bvFTD remains challenging because of the limited accuracy of neuroimaging in the early disease stages and the absence of molecular biomarkers, and therefore relies predominantly on clinical assessment. BvFTD shows significant symptomatic overlap with non-degenerative primary psychiatric disorders including major depressive disorder, bipolar disorder, schizophrenia, obsessive-compulsive disorder, autism spectrum disorders and even personality disorders. To date, ∼50% of patients with bvFTD receive a prior psychiatric diagnosis, and average diagnostic delay is up to 5–6 years from symptom onset. It is also not uncommon for patients with primary psychiatric disorders to be wrongly diagnosed with bvFTD. The Neuropsychiatric International Consortium for Frontotemporal Dementia was recently established to determine the current best clinical practice and set up an international collaboration to share a common dataset for future research. The goal of the present paper was to review the existing literature on the diagnosis of bvFTD and its differential diagnosis with primary psychiatric disorders to provide consensus recommendations on the clinical assessment. A systematic literature search with a narrative review was performed to determine all bvFTD-related diagnostic evidence for the following topics: bvFTD history taking, psychiatric assessment, clinical scales, physical and neurological examination, bedside cognitive tests, neuropsychological assessment, social cognition, structural neuroimaging, functional neuroimaging, CSF and genetic testing. For each topic, responsible team members proposed a set of minimal requirements, optimal clinical recommendations, and tools requiring further research or those that should be developed. Recommendations were listed if they reached a ≥ 85% expert consensus based on an online survey among all consortium participants. New recommendations include performing at least one formal social cognition test in the standard neuropsychological battery for bvFTD. We emphasize the importance of 3D-T₁ brain MRI with a standardized review protocol including validated visual atrophy rating scales, and to consider volumetric analyses if available. We clarify the role of ¹⁸F-fluorodeoxyglucose PET for the exclusion of bvFTD when normal, whereas non-specific regional metabolism abnormalities should not be over-interpreted in the case of a psychiatric differential diagnosis. We highlight the potential role of serum or CSF neurofilament light chain to differentiate bvFTD from primary psychiatric disorders. Finally, based on the increasing literature and clinical experience, the consortium determined that screening for C9orf72 mutation should be performed in all possible/probable bvFTD cases or suspected cases with strong psychiatric features.

中文翻译：

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区分行为变异型额颞叶痴呆和精神疾病的建议。

额颞叶痴呆（bvFTD）的行为变异是早发性痴呆的常见原因。由于早期疾病阶段神经影像学的准确性有限且缺乏分子生物标志物，bvFTD 的诊断仍然具有挑战性，因此主要依赖于临床评估。BvFTD 显示出与非退行性原发性精神疾病显着的症状重叠，包括重度抑郁症、双相情感障碍、精神分裂症、强迫症、自闭症谱系障碍甚至人格障碍。迄今为止，约 50% 的 bvFTD 患者之前接受过精神病学诊断，从症状出现起平均诊断延迟长达 5-6 年。原发性精神疾病患者被错误诊断为 bvFTD 的情况也并不罕见。额颞叶痴呆神经精神病学国际联盟最近成立，旨在确定当前的最佳临床实践，并建立国际合作以共享未来研究的通用数据集。本文的目的是回顾有关 bvFTD 诊断及其与原发性精神疾病鉴别诊断的现有文献，为临床评估提供共识建议。通过叙述性回顾进行系统文献检索，以确定以下主题的所有 bvFTD 相关诊断证据：bvFTD 病史采集、精神病学评估、临床量表、身体和神经学检查、床旁认知测试、神经心理学评估、社会认知、结构神经影像、功能神经影像、脑脊液和基因检测。对于每个主题，负责的团队成员提出了一组最低要求、最佳临床建议以及需要进一步研究或应该开发的工具。根据对所有联盟参与者的在线调查，如果达到 ≥ 85% 的专家共识，就会列出建议。新的建议包括在 bvFTD 的标准神经心理学电池中进行至少一项正式的社会认知测试。_{我们强调 3D-T 1}脑 MRI的重要性以及标准化审查方案（包括经过验证的视觉萎缩评级量表），并考虑体积分析（如果有）。^{我们阐明了18} F-氟脱氧葡萄糖 PET 在正常情况下排除 bvFTD 的作用，而在精神科鉴别诊断的情况下，不应过度解释非特异性区域代谢异常。我们强调血清或脑脊液神经丝轻链在区分 bvFTD 和原发性精神疾病方面的潜在作用。最后，根据不断增加的文献和临床经验，该联盟确定筛选C9orf72应在所有可能/可能的 bvFTD 病例或具有强烈精神特征的疑似病例中进行突变。