ImportanceItching is common in geriatric populations and is frequently linked to dermatological or systemic conditions. Itching engages specific brain regions that are implicated in the pathogenesis of frontotemporal lobar degeneration spectrum disorders (FTLD-SD). Thus, itching of undetermined origin (IUO) may indicate the presence of a neurodegenerative process.ObjectiveTo compare the frequency of itching in FTLD-SD and Alzheimer disease (AD) and to determine the neuroanatomical underpinnings of IUO.Design, Setting, and ParticipantsThis case-control study evaluated data and brain magnetic resonance images (MRIs) for participants with FTLD-SD or AD. Participants of a research study on FTLD-SD at the University of California, San Francisco, Memory and Aging Center were evaluated from May 1, 2002, to December 31, 2021. The exposure group underwent structural brain MRI within 6 months of initial diagnosis. Research visit summaries were reviewed to validate qualitative details and accurately identify itching with undetermined origin (IUO).ExposuresSymptoms suggestive of FTLD-SD or AD.Main Outcomes and MeasuresFrequency of itching in FTLD-SD and AD and neuroanatomic correlates.ResultsA total of 2091 research visit summaries were reviewed for 1112 patients exhibiting symptoms indicative of FTLD-SD or AD. From 795 records where itching or a related phrase was endorsed, 137 had IUO. A total of 454 participants were included in the study: 137 in the itching group (mean [SD] age, 62.7 [9.9] years; 74 [54%] females and 63 males [46%]) and 317 in the nonitching group (mean [SD] age, 60.7 [10.8] years; 154 [49%] females and 163 males [51%]). Groups were similar in age, sex, and disease severity. More frequent itching was found in FTLD-SD (95/248 patients [38%], of which 44 [46%] had behavioral variant frontotemporal dementia [bvFTD]) compared with the AD group (14/77 patients [18%]; P = .001). The odds of itching were 2.4 (95% CI, 1.48-3.97) times higher for FTLD-SD compared with all other cases of dementia. Compared with healthy controls, the group with IUO exhibited greater gray matter atrophy bilaterally in the amygdala, insula, precentral gyrus, and cingulum, as well as in the right frontal superior gyrus and thalamus. Among patients with bvFTD and itching vs bvFTD without itching, itching was associated with right-lateralized gray matter atrophy affecting the insula, thalamus, superior frontal gyrus, and cingulum.Conclusions and RelevanceAmong individuals with IUO, FTLD-SD was disproportionately represented compared with AD. In FTLD-SD, dysfunction in the right anterior insula and its connected regions, including the right precentral gyrus, cingulum, and bilateral amygdala, contribute to dysregulation of the itching-scratching networks, resulting in uncontrollable itching or skin picking. Awareness among physicians about the relationship between neurodegeneration and itching may help in the management of itch in older individuals. Further studies are needed to determine the best treatments for these symptoms in patients with neurodegenerative disorders.

中文翻译：

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额颞叶变性的瘙痒频率与神经解剖学相关性


重要性瘙痒在老年人群中很常见，并且常常与皮肤病或全身性疾病有关。瘙痒涉及特定的大脑区域，这些区域与额颞叶变性谱系障碍（FTLD-SD）的发病机制有关。因此，不明原因瘙痒 (IUO) 可能表明存在神经退行性过程。目的比较 FTLD-SD 和阿尔茨海默病 (AD) 中瘙痒的频率，并确定 IUO 的神经解剖学基础。设计、设置和参与者本案例-对照研究评估了 FTLD-SD 或 AD 参与者的数据和脑部磁共振图像 (MRI)。加州大学旧金山分校记忆与衰老中心的 FTLD-SD 研究参与者于 2002 年 5 月 1 日至 2021 年 12 月 31 日期间接受了评估。暴露组在初次诊断后 6 个月内接受了结构性脑 MRI。审查研究访问摘要，以验证定性细节并准确识别不明原因的瘙痒 (IUO)。暴露提示 FTLD-SD 或 AD 的症状。主要结果和措施 FTLD-SD 和 AD 中瘙痒的频率以及神经解剖学相关性。结果总共 2091 项研究对 1112 名表现出 FTLD-SD 或 AD 症状的患者的就诊总结进行了审查。在 795 条认可“痒”或相关短语的记录中，有 137 条包含 IUO。该研究共有 454 名参与者：瘙痒组 137 名（平均 [SD] 年龄，62.7 [9.9] 岁；女性 74 名 [54%]，男性 63 名 [46%]），非瘙痒组 317 名（平均 [SD] 年龄，60.7 [10.8] 岁；女性 154 [49%]，男性 163 [51%]）。各组的年龄、性别和疾病严重程度相似。 与 AD 组（14/77 例患者 [18%]）相比，FTLD-SD 组（95/248 例患者 [38%]，其中 44 例 [46%] 患有行为变异型额颞叶痴呆 [bvFTD]）瘙痒更频繁； P = .001)。与所有其他痴呆病例相比，FTLD-SD 出现瘙痒的几率高出 2.4 倍（95% CI，1.48-3.97）。与健康对照组相比，IUO组的双侧杏仁核、岛叶、中央前回和扣带回以及右额上回和丘脑的灰质萎缩程度更大。在有瘙痒的 bvFTD 患者与无瘙痒的 bvFTD 患者中，瘙痒与影响岛叶、丘脑、额上回和扣带回的右侧灰质萎缩有关。结论和相关性在 IUO 个体中，与 AD 相比，FTLD-SD 的比例不成比例。在 FTLD-SD 中，右前岛叶及其连接区域（包括右中央前回、扣带回和双侧杏仁核）的功能障碍会导致瘙痒-抓挠网络失调，导致无法控制的瘙痒或皮肤抓痒。医生对神经退行性变和瘙痒之间关系的认识可能有助于控制老年人的瘙痒。需要进一步的研究来确定神经退行性疾病患者这些症状的最佳治疗方法。