[Imaging of brain acetylcholinesterase activity in dementias and extrapyramidal disorders]

Carbon-11 labeled N-methylpiperidin-4-yl acetate ([11C]MP4A) and carbon-11 labeled N-methylpiperidin-4-yl propionate ([11C]MP4P) are acetylcholine analogues and have been successfully used for measurement of brain acetylcholinesterase (AChE) activity in vivo in humans. In Alzheimer's disease (AD), there is a significant loss of AChE activity in the cerebral cortex in association with mental decline. The reduction of AChE activity in the cerebral cortex is more remarkable in early-onset AD than late-onset AD. There is mild but significant reduction of AChE activity in the cerebral cortex, even in the early stage of Parkinson's disease (PD) without dementia. There is remarkable reduction of AChE activity in the entire cerebral cortex in both PD with dementia and dementia with Lewy bodies (DLB). In two patients with frontotemporal dementia with parkinsonism linked to chromosome 17, there was prominent reduction of AChE activity in the cerebral cortex and thalamus. In 12 patients with progressive supranuclear palsy, there was profound reduction of AChE activity in the thalamus but not in the cerebral cortex. In corticobasal degeneration, there is symmetrical loss of AChE activity in the sensori-motor cortex.