研究背景：脊髓小脑共济失调（SCA）是一组具有遗传异质性的常染色体显性遗传病，有些类型为多个部位受累，伴发非小脑症状，如SCA1、SCA2、SCA3；有些类型为纯小脑症状，如SCA6。

研究目的：分析SCA1、SCA2、SCA3和SCA6患者中枢神经系统多巴胺能系统和区域葡萄糖代谢异常。

方法：以[ 11C]d-threo-methylphenidate 和[18F]fluorodeoxyglucose作为示踪剂的PET检查，以识别大脑多巴胺能神经末梢和特定区域的代谢水平。

结果：SCA2和SCA3患者纹状体对[11C]d-threo-methylphenidate的结合能力下降，与帕金森病患者相比，在壳核没有明显升高。SCA患者小脑区域葡萄糖代谢水平均降低，其他代谢水平下降的部位包括SCA1、SCA2、SCA3患者的脑干部位，SCA3患者的丘脑和壳核部位，SCA2患者大脑顶叶皮层。在SCA1、SCA2、SCA3和SCA6均可见颞叶皮层葡萄糖代谢水平升高，尤其是SCA6。

结论：SCA1、SCA2、SCA3和SCA6各自不同的特异性生化改变提示神经功能异常的不同机制；多巴胺神经末梢在SCA2减少最为明显，但是有别于帕金森病。

原文：

Wüllner U, Reimold M, Abele M, et al. Dopamine transporter positron emission tomography in spinocerebellar ataxias type 1, 2, 3, and 6. Arch Neurol. 2005 Aug;62(8):1280-5.

BACKGROUND: The spinocerebellar ataxias (SCAs) are a genetically heterogeneous group of autosomal dominant ataxias: some mutations, including SCA1, SCA2, and SCA3, are multisystemic disorders characterized by a variety of noncerebellar symptoms while others, like SCA6, give rise to a pure cerebellar syndrome.

OBJECTIVE: To identify impairments of the dopaminergic system and regional changes of glucose metabolism in SCA1, SCA2, SCA3, and SCA6.

METHODS: We used [11C]d-threo-methylphenidate and [18F]fluorodeoxyglucose positron emission tomography to identify cerebral dopamine terminal loss and specific regional metabolic patterns in SCA1, SCA2, SCA3, and SCA6.

RESULTS: The binding potential of [11C]d-threo-methylphenidate was reduced in the striatum in SCA2 and SCA3; in contrast to patients with Parkinson disease, no increased susceptibility of the putamen was evident. Decreased regional cerebral glucose metabolism was found in the cerebellum of all patients with SCA, the brainstem of SCA1, SCA2, SCA3, the thalamus and putamen of SCA3, and the parietal cortex of patients with SCA2. A trend toward increased regional cerebral glucose metabolism was found in the temporal cortex of all patients with SCA, pronounced in SCA6.

CONCLUSIONS: Specific biochemical patterns point to different mechanisms of neuronal dysfunction in SCA1, SCA2, SCA3, and SCA6; dopamine terminal loss is severe in SCA2 but distinct from Parkinson disease.

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