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Original Investigation
November 2016

Tau Positron Emission Tomographic Imaging in the Lewy Body Diseases

Author Affiliations
  • 1MassGeneral Institute for Neurodegenerative Disease, Charlestown, Massachusetts
  • 2Alzheimer’s Disease Research Center, Department of Neurology, Massachusetts General Hospital and Harvard Medical School, Charlestown
  • 3Frontotemporal Disorders Unit, Department of Neurology, Massachusetts General Hospital and Harvard Medical School, Charlestown
  • 4Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital and Harvard Medical School, Charlestown
  • 5Division of Nuclear Medicine and Molecular Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston
JAMA Neurol. 2016;73(11):1334-1341. doi:10.1001/jamaneurol.2016.3338
Key Points

Question  Do tau pathologic changes relate to clinical status and amyloid deposition in the Lewy body diseases?

Findings  In this cross-sectional positron emission tomographic imaging study of 24 patients with Lewy body disease (including participants with dementia with Lewy bodies [DLB], as well as cognitively impaired and cognitively normal individuals with Parkinson disease [PD]) and 29 healthy individuals with low brain amyloid levels, cortical fluorine 18–labeled AV-1451 ([18F]AV-1451) uptake was increased in patients with DLB and PD and related to greater cognitive functional impairment. Elevated neocortical tau was observed in some patients with low amyloid burden, imaged with carbon 11–labeled Pittsburgh Compound B.

Meaning  Neocortical tau pathology is common in DLB- and PD-impaired patients, even in the absence of elevated brain amyloid deposition, and contributes to cognitive impairment.

Abstract

Importance  The causes of cognitive impairment in dementia with Lewy bodies (DLB) and Parkinson disease (PD) are multifactorial. Tau pathologic changes are commonly observed at autopsy in individuals with DLB and PD dementia, but their contribution to these diseases during life is unknown.

Objective  To contrast tau aggregation in DLB, cognitively impaired persons with PD (PD-impaired), cognitively normal individuals with PD (PD-normal), and healthy persons serving as control participants, and to evaluate the association between tau aggregation, amyloid deposition, and cognitive function.

Design, Setting, and Participants  This cross-sectional study was conducted from January 1, 2014, to April 28, 2016, in a tertiary care center’s memory and movement disorders units. Twenty-four patients with Lewy body disease (7 DLB, 8 PD-impaired, and 9 PD-normal) underwent multimodal brain imaging, cognitive testing, and neurologic evaluation, and imaging measures were compared with those of an independently acquired group of 29 controls with minimal brain amyloid burden as measured with carbon 11–labeled Pittsburgh Compound B ([11C]PiB) positron emission tomography (PET).

Exposures  Imaging with fluorine 18–labeled AV-1451 ([18F]AV-1451) (formerly known as [18F]T807), [11C]PiB PET, magnetic resonance imaging (MRI), neurologic examination, and detailed cognitive testing using the Mini-Mental State Examination (MMSE) and Clinical Dementia Rating scale.

Main Outcomes and Measures  Main outcomes were differentiation of diagnostic groups on the basis of [18F]AV-1451 binding, the association of [18F]AV-1451 binding with [11C]PiB binding, and the association of [18F]AV-1451 binding with cognitive impairment. All but 3 individuals underwent amyloid imaging with [11C]PiB PET. The hypotheses being tested were formulated before data collection. Mini-Mental State Examination (range, 0-30, with 30 being best) and Clinical Dementia Rating scale sum-of-boxes scale (range, 0-18, with 0 being best) were used for assessment of cognitive function.

Results  In patients with DLB, cortical [18F]AV-1451 uptake was highly variable and greater than in the controls, particularly in the inferior temporal gyrus and precuneus. Foci of increased [18F]AV-1451 binding in the inferior temporal gyrus and precuneus were also evident in PD-impaired patients. Elevated cortical [18F]AV-1451 binding was observed in 4 of 17 patients with Lewy body disease with low cortical [11C]PiB retention. For DLB and PD-impaired patients, greater [18F]AV-1451 uptake in the inferior temporal gyrus and precuneus was associated with increased cognitive impairment as measured with the MMSE and the Clinical Dementia Rating scale sum-of-boxes score.

Conclusions and Relevance  Patients with Lewy body disease manifest a spectrum of tau pathology. Cortical aggregates of tau are common in patients with DLB and in PD-impaired patients, even in those without elevated amyloid levels. When present, tau deposition is associated with cognitive impairment. These findings support a role for tau copathology in the Lewy body diseases.

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