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Abstract
Objective: The aim of our study was to examine the relationship between corticostriatal Aβ-amyloid deposition and cognitive dysfunction in a cohort of patients with Parkinson disease (PD) at risk for dementia.
Methods: This was a cross-sectional study of 40 patients with PD with mild cognitive impairment (MCI) or other known dementia risk factors. Subjects underwent dynamic Aβ-amyloid and vesicular monoamine transporter 2 PET imaging using [11C] Pittsburgh compound B (PiB) and [11C]dihydrotetrabenazine (DTBZ), respectively, and neuropsychological assessment. PiB and DTBZ PET data were analyzed using the Logan graphical method to determine cerebral PiB deposition relative to the cerebellar hemispheres and striatal DTBZ binding relative to occipital neocortex. Component z scores were calculated for individual cognitive domains (memory, visuospatial processing, working memory/attention, and executive function) and combined linearly for global estimation of cognition. Correlation of cognitive function and cortical PiB binding was investigated.
Results: Elevated cerebral PiB binding at levels seen in patients with AD was infrequent (6 of 40 subjects). Mean cortical PiB binding in the entire cohort was 1.16 ± 0.16 (distribution volume ratio; range 0.96–1.78). A significant correlation was noted between cortical PiB binding and global composite cognitive function (r = −0.55, p < 0.005) as well as the Wechsler Adult Intelligence Scale score (r = −0.54, p = 0.0004).
Conclusion: Elevated cerebral Aβ-amyloid deposition at levels seen in Alzheimer disease is uncommon in subjects with PD at risk for dementia. In our sample, the prevalence of markedly elevated PiB binding was significantly lower than that found in prior studies of cognitively normal elderly individuals. Neocortical PiB binding correlated robustly with measures of cognitive impairment in our cohort.
GLOSSARY
- AD=
- Alzheimer disease;
- DLB=
- dementia with Lewy bodies;
- DTBZ=
- dihydrotetrabenazine;
- DVR=
- distribution volume ratio;
- MCI=
- mild cognitive impairment;
- MOCA=
- Montreal Cognitive Assessment;
- PCA=
- principal component analysis;
- PiB=
- Pittsburgh compound B;
- PD=
- Parkinson disease;
- PDD=
- Parkinson disease dementia;
- UPDRS=
- Unified Parkinson's Disease Rating Scale;
- VOI=
- volume of interest;
- WAIS=
- Wechsler Adult Intelligence Scale
Footnotes
Study funding: Supported by the NIH (grants P01-NS015655 and R01-NS070856), the RSNA Research and Education Foundation, and the Michael J. Fox Foundation.
- Received January 17, 2012.
- Accepted April 19, 2012.
- Copyright © 2012 by AAN Enterprises, Inc.
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