DOES CEREBRAL GLUCOSE METABOLISM AND BLOOD FLOW DISSOCIATE IN EARLY STAGES OF ALZHEIMER'S DISEASE?

Abstract

Background: Mild cognitive impairment (MCI) patients with different biomarker profiles might be characterized by different patterns of cortical thinning and subcortical atrophy. Methods: 53 MCI patients (mean age 71, female 49%) were enrolled from 2 Italian Memory Clinics. Abeta42 and Tau CSF levels, temporo parietal hypometabolism and hippocampal volumes were measured. According to their biormarker profiles, patients were divided in two groups: (i) suspected n on-amyloid pathology (SNAP, N1⁄421) and (ii) patients with amyloid plus neurodegeneration (A+N, N1⁄432). Cortical thickness and sucortical volumes were quantified using the freesurfer pipeline. Comparisons were made at group level with 15 subjective memory complainers (SMC), considered as the control group. Results: SMC were cognitively intact, younger than SNAP and A+N patients (p<.006). Relative to SMC group, A+N showed cortical thinning in the left/right parietal inferior and superior regions (p<.028), temporal middle and superior temporo-lateral gyri (p1⁄4.05), left inferior frontal gyrus (p1⁄4.009), right lateral fusyform gyrus (p<.002), insula and precentral sulcus (p1⁄4.01). SNAP patients compared to SMC exhibited cortical thinning in the left central sulcus (p1⁄4.025), right superior and inferior tempro-lateral (p<.002) and parietal gyri (p1⁄4.04), and precentral sulcus (p1⁄4.011). The direct comparison between A+N and SNAP showed significant cortical thinning only in the A+N group in the right and left lateral fusyform gyrus (p<.039), left occipital middle and lingual gyri (p1⁄4.020 and p1⁄4.007), parietal regions (p<.049) and orbito-lateral sulcus (p1⁄4.041). Both SNAP and A+N groups compared to SMC showed substantial subcortical volume reductions bilaterally in the hippocampus (p<.05), the nucleus accumbens (p<.046), the right pallidum (p<.0401), the left amygdala (p<.005). The direct comparisons between the two patient groups revealed a significant right amygdala atrophy in A+N patients. Conclusions: Our results support the hypothesis that SNAP patients are characterized by a different cortical and subcortical involvement relative to A+N due to different underlying pathologic changes.