Background

Excessive exposure to manganese (Mn) may cause parkinsonian-like motor and tremor symptoms and adverse cognitive effects, including problems with executive functioning (EF), resembling those found in later-stage Parkinson’s disease (PD). Studies seeking to differentiate PD patients into subgroups with associated cognitive and functional outcomes using motor and tremor symptoms identified tremor-dominant (TD) and non-tremor dominant (NTD) subtypes. It is unclear whether differing patterns of pathophysiology and symptoms exist in Mn neurotoxicity, as they do in PD.

Methods

Residents of East Liverpool (n = 83) and Marietta, OH (n = 99) exposed to chronic (>10 years) environmental Mn through industrial pollution were administered neuropsychological measures and a physician-rated scale of movement-disorder symptoms. Two-step cluster analysis was used to group residents based on tremor symptoms, bradykinesia/rigidity symptoms, gait disturbance, and executive function. Cluster membership was validated using modeled air-Mn exposure and a computerized tremor measure.

Results

Elevated tremor and motor symptoms and executive dysfunction were observed, and TD and NTD symptom clusters were identified. Two additional clusters were also identified: Executive Dysfunction and Normal Functioning. The NTD residents, with elevated levels of gait disturbance and other movement disorder symptoms, did not evidence EF impairment, as predicted. Instead, residents with EF impairment formed their own cluster, and were relatively free of movement disorder symptoms.

Conclusions

Results resemble reports in the PD literature with TD and NTD clusters identified, but executive dysfunction did not cluster with NTD symptoms. PD and Mn exposure likely have differing pathophysiology and developmental courses, and therefore different symptom patterns, even when similar symptoms are present.

中文翻译：

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空气中锰的环境暴露：震颤、运动和认知症状特征

背景

过量接触锰 (Mn) 可能会导致帕金森病样运动和震颤症状以及不良认知影响，包括执行功能 (EF) 问题，类似于晚期帕金森病 (PD) 中发现的问题。研究试图利用运动和震颤症状将 PD 患者分为与认知和功能结果相关的亚组，确定了震颤主导型 (TD) 和非震颤主导型 (NTD) 亚型。目前尚不清楚锰神经毒性是否与帕金森病一样存在不同的病理生理学和症状模式。

方法

东利物浦 (n = 83) 和俄亥俄州玛丽埃塔 (n = 99) 的居民因工业污染而长期（>10 年）接触环境锰，接受了神经心理学测量和医生评定的运动障碍症状量表。采用两步聚类分析根据震颤症状、运动迟缓/强直症状、步态障碍和执行功能对居民进行分组。使用模型化的空气-锰暴露和计算机化的震颤测量来验证簇成员资格。

结果

观察到震颤和运动症状加重以及执行功能障碍，并确定了 TD 和 NTD 症状群。还确定了另外两个集群：执行功能障碍和正常功能。NTD 居民的步态障碍和其他运动障碍症状水平较高，但并未像预测的那样出现 EF 损伤。相反，患有 EF 障碍的居民形成了自己的群体，并且相对没有运动障碍症状。

结论

结果类似于 PD 文献中的报告，其中确定了 TD 和 NTD 集群，但执行功能障碍并不与 NTD 症状集群。PD 和锰暴露可能具有不同的病理生理学和发育过程，因此即使存在相似的症状，也可能具有不同的症状模式。