Non-Alzheimer's amnestic mild cognitive impairment with medial temporal hypometabolism

Abstract

INTRODUCTION: The increasing use of Alzheimer's disease (AD) biomarkers has led to the recognition of a subgroup of non-AD amnestic mild cognitive impairment (aMCI) patients who have medial temporal hypometabolism on fluorodeoxyglucose-positron emission tomography (FDG-PET). METHODS: In this academic memory-clinic-based consecutive series, 16 non-AD aMCI patients and 28 AD controls matched for sex, age, and baseline Mini-Mental State Examination (MMSE) were followed for a median duration of 4.5 years. Our primary outcome was the MMSE decline rate over the subsequent years. We also determined the final diagnosis over time. RESULTS: FDG-PET showed more pronounced medial temporal hypometabolism in non-AD cases and more inferior parietal lobule hypometabolism in AD controls. MMSE decline was slower in non-AD (β = −0.51) than in AD (β = −2.00) patients. Five non-AD cases developed frontotemporal dementia years after symptom onset, and one developed dementia with Lewy bodies. DISCUSSION: Non-AD aMCI patients with medial temporal hypometabolism show slower cognitive decline. Highlights: Non-AD aMCI with medial temporal hypometabolism shows slower cognitive decline than AD. FDG-PET revealed distinct metabolic patterns between non-AD aMCI and AD patients. Approximately one-third of non-AD aMCI cases developed frontotemporal dementia. Comprehensive diagnostic biomarkers are crucial for non-AD aMCI characterization.