Abstract
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Objectives Several neurodegenerations are responsible for cognitive decline and dementia. Routine clinical assessments do not accurately identify the etiology of dementia early in its course. We evaluated PET neurochemical measures of Aß-amyloidosis and of nigrostriatal projection integrity for classification of mild-early dementia.
Methods Sixty-six patients with mild cognitive impairment or mild dementia (MMSE ≥ 18) were identified from a Cognitive Disorders clinic. Subjects underwent neurological, neuropsychometric, and anatomic brain imaging examinations. Three experts reviewed abstracted results of these data and reached consensus clinical diagnoses: Alzheimer disease (AD); frontotemporal dementia (FTD); or dementia with Lewy bodies (DLB). PET imaging with [11C]PiB for amyloid deposition and [11C]DTBZ for nigrostriatal projection integrity was performed. PET classified subjects as FTD if both PiB and DTBZ were normal, as DLB if severe striatal DTBZ defects were present, or as AD if DTBZ was normal and frontal cortical PiB binding was increased.
Results There was discordance of clinical and PET classifications in 26% of subjects.
Results Three of 9 patients with nigrostriatal PET lesions were unrecognized clinically. Nine of 43 PiB-positive patients were missed clinically, and 3 of 14 FTD patients were clinically classified as AD.
Conclusions There are frequent differences in the phenotypic classification of dementia by clinical criteria in comparison to PET. Neurochemical imaging could contribute significantly to the safety and appropriateness of treatment in mild-early dementia.
- © 2009 by Society of Nuclear Medicine