Meyer Michael A, Caccia Allison, Martinez Danielle, Mingos Mark A
Departments of Neurology and Nuclear Medicine, Guthrie Clinic, Sayre PA, USA.
Neurol Int. 2018 Sep 25;10(3):7666. doi: 10.4081/ni.2018.7666. eCollection 2018 Sep 5.
Ten individuals suspected of having possible Alzheimer disease underwent PET imaging using 18F-Flubetapir. Only one of ten individuals had a pattern typical for normal elderly control subjects with 9 of the 10 showing a Alzheimer type pattern for the cerebral cortex yet all 10 subjects had uniformly low to absent tracer localization to the cerebellar cortex; significantly high tracer activity was noted within the subcortical white matter of the cerebellum in a symmetric manner in all cases. In consideration of studies that have shown amyloid deposits within the cerebellar cortex in 90% of pathologically proven cases of Alzheimer's disease, these findings raise questions about the actual clinical value of florbetapir PET imaging in evaluating cerebellar involvement and raises questions whether PET imaging of this tracer accurately portrays patterns of amyloid deposition, as there is rapid hepatic metabolism of the parent compound after intravenous injection. Possible links to Alzheimer's disease related alterations in blood-brain barrier permeability to the parent compound and subsequent radiolabelled metabolites are discussed as potential mechanisms that could explain the associated localization of the tracer to the brainstem and subcortical white matter within the cerebrum and cerebellum of Alzheimer's disease patients.
十名疑似患有阿尔茨海默病的个体使用18F-氟比他哌进行了PET成像。十名个体中只有一名具有正常老年对照受试者的典型模式，十名中的九名显示出大脑皮质的阿尔茨海默病类型模式，但所有10名受试者的小脑皮质示踪剂定位均一致偏低或缺失；在所有病例中，均观察到小脑皮质下白质内有明显的示踪剂高活性，呈对称分布。考虑到研究表明，在90%经病理证实的阿尔茨海默病病例的小脑皮质中有淀粉样蛋白沉积，这些发现对氟比他哌PET成像在评估小脑受累方面的实际临床价值提出了疑问，并对这种示踪剂的PET成像是否能准确描绘淀粉样蛋白沉积模式提出了疑问，因为静脉注射后母体化合物会迅速发生肝脏代谢。讨论了与阿尔茨海默病相关的血脑屏障对母体化合物及随后放射性标记代谢物通透性改变的可能联系，作为可能解释阿尔茨海默病患者大脑和小脑脑干及皮质下白质中示踪剂相关定位的潜在机制。
