Brain metabolic patterns and amyloid brain deposition at 5 years follow-up in patients with amnestic mild cognitive impairment as assessed by 11 C-PIB and 18 F-FDG PET/CT

Abstract

Background: To assess 5-year changes in regional brain metabolic patterns by ¹⁸F-FDG PET/CT in amnestic mild cognitive impairment (A-MCI) patients and link these changes to clinical outcomes and initial ¹¹C-PIB PET/CT findings. Methods: In 65 A-MCI patients diagnosed using ¹¹C-PIB and 18F-FDG PET/CT, a 5-year follow-up began. 34 patients underwent new ¹¹C-PIB and ¹⁸F-FDG PET/CT scans, analyzing global and regional brain amyloid load (BAL) and glucose brain metabolism (GBM) across 26 selected brain regions. Clinical status was assessed using the Global Deterioration Scale (GDS) and neuropsychological tests. Additionally, 73 healthy volunteers formed the control group, undergoing ¹⁸F-FDG PET/CT scans. Results: Follow-up at 5 years involved 65 A-MCI patients. Among the 34 re-evaluated (27 PIB positive, 7 negative initially), global BAL increased by 22% and GBM decreased by 1.4%, notably in specific brain regions. In the 27 PIB positive patients, two cerebral metabolic patterns emerged: 13/27 showed reduced global GBM (mean: -11.25%) and 14/27 showed no reduction (mean: 8.80%) (p<0.05), with regional variations. Moderate correlations were found between regional BAL and GBM (r= -0.378 and 0.336). Clinical progress at 5 years for PIB positive A-MCI (GDS3): one remained A-MCI, 10 developed mild-AD (GDS4), 10 moderate-AD (GDS5), and 6 severe-AD (GDS6). Among the 7 PIB negative A-MCI (GDS3), 5 remained GDS3, and 2 developed other dementias. Conclusions: At 5 years, A-MCI patients with brain amyloid showed diverse glucose metabolic changes, involving global and regional hypermetabolism linked to varying cognitive statuses.