Analysis of the posterior cingulate cortex with [18F]FDG-PET and Naa/mI in mild cognitive impairment and Alzheimer's disease: Correlations and differences between the two methods.

Artur M.N Coutinho,Rafael F Nunes,Carlos A Buchpiguel,Tíbor R Perroco,Toulouse Leusin Pinheiro,Maira O Oliveira,Fábio H.G Porto,Cassio M.C Bottino,Poliana F Zampieri,Claudia C Leite,Maria C Otaduy

doi:10.1590/1980-57642015dn94000385

Abstract

Reduction of regional brain glucose metabolism (rBGM) measured by [18F]FDG-PET in the posterior cingulate cortex (PCC) has been associated with a higher conversion rate from mild cognitive impairment (MCI) to Alzheimer's disease (AD). Magnetic Resonance Spectroscopy (MRS) is a potential biomarker that has disclosed Naa/mI reductions within the PCC in both MCI and AD. Studies investigating the relationships between the two modalities are scarce.ObjectiveTo evaluate differences and possible correlations between the findings of rBGM and NAA/mI in the PCC of individuals with AD, MCI and of cognitively normal volunteers.MethodsPatients diagnosed with AD (N=32) or MCI (N=27) and cognitively normal older adults (CG, N=28), were submitted to [18F]FDG-PET and MRS to analyze the PCC. The two methods were compared and possible correlations between the modalities were investigated.ResultsThe AD group exhibited rBGM reduction in the PCC when compared to the CG but not in the MCI group. MRS revealed lower NAA/mI values in the AD group compared to the CG but not in the MCI group. A positive correlation between rBGM and NAA/mI in the PCC was found. NAA/mI reduction in the PCC differentiated AD patients from control subjects with an area under the ROC curve of 0.70, while [18F]FDG-PET yielded a value of 0.93.ConclusionrBGM and Naa/mI in the PCC were positively correlated in patients with MCI and AD. [18F]FDG-PET had greater accuracy than MRS for discriminating AD patients from controls.

Highlights

Alzheimer’s disease (AD) has become a public health problem with the rise in life expectancy, since there is currently no treatment that modifies its progression.[1,2,3] Correct diagnosis in the early stages of the disease is crucial to better understand its pathophysiology and to develop treatments to slow its progression
Subjects included in the control group (CG) were younger (p
The AD group exhibited regional brain glucose metabolism (rBGM) reduction in large areas of the posterior cingulate cortex (PCC) and temporoparietal cortex compared to the CG, and in less evident areas of the frontal cortex

Summary

Introduction

Alzheimer’s disease (AD) has become a public health problem with the rise in life expectancy, since there is currently no treatment that modifies its progression.[1,2,3] Correct diagnosis in the early stages of the disease is crucial to better understand its pathophysiology and to develop treatments to slow its progression. Mild cognitive impairment (MCI), especially the amnestic subtype, is a symptomatic transitional state from normal aging to early dementia. MCI is characterized by subjective memory complaints and objective decline in cognitive performance, with normal or near-normal functional activities of daily living.[4,5]. A progressive reduction of rBGM in specific areas occurs years before the onset of clinical symptoms in patients with verified AD and during the MCI phase, in the temporoparietal cortex and posterior cingulate cortex (PCC) association.[6,7,8,9,10] Of all the areas, the PCC seems to be the most sensitive marker for predicting which patients with MCI will progress to AD.[7,10,11]

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