Jennifer Rose V. Molano, MD reviewing Johnson KA et al. Ann Neurol 2016 Jan.
Tau imaging may be a new biomarker in Alzheimer disease.

To investigate 18F T807 as a biomarker for tau pathology in Alzheimer disease (AD), researchers recruited 75 participants of the Harvard Aging Brain Study. Of the 75 patients (mean age, 73), 56 were cognitively normal, 13 had mild cognitive impairment (MCI), and 6 had dementia based on clinical evaluation that included the Mini-Mental State Examination, Clinical Dementia Rating scale, and Logical Memory delayed recall test. Tau deposition was identified using standardized uptake value ratio from 18F T807 positron emission tomography imaging, and amyloid deposition was identified using distribution volume ratio from 11C Pittsburgh Compound B (PiB) imaging.

Corresponding to the Braak neuropathology staging scheme for AD, tau deposition was minimal or localized to the medial temporal lobe in the cognitively normal group, and greater tau deposition in the temporal and neocortical areas was seen in the participants with MCI and dementia. Compared with the cognitively normal group, the MCI/dementia group had greater tau deposition in the entorhinal and parahippocampal regions, but not in the hippocampus. Tau deposition in the inferior temporal and fusiform regions was also lowest in cognitively normal participants and highest in those with dementia. Greater inferior temporal tau binding and mean cortical PiB binding was associated with greater impairment on all clinical evaluation measures in those with MCI/dementia. Greater inferior temporal 18F T807 binding also was associated with higher mean cortical PiB binding in the entire sample. The researchers concluded that 18F T807 can be a useful biomarker for tau pathology and clinical impairment in AD.

Citation(s):

Johnson KA et al. Tau positron emission tomographic imaging in aging and early Alzheimer's disease. Ann Neurol 2016 Jan; 79:110.

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