Clinical, Neuropsychological, and Neuroimaging Characteristics of Amyloid- positive vs. Amyloid-negative Patients with Clinically Diagnosed Alzheimer’s Disease and Amnestic Mild Cognitive Impairment

Background: A significant proportion of patients with clinically diagnosed Alzheimer’s Disease (AD) and an even higher proportion of patients with amnestic mild cognitive impairment (aMCI) do not show evidence of amyloid deposition on Positron Emission Tomography (PET) with amyloid-binding tracers such as 11 C-labeled Pittsburgh Compound B (PiB). Objective: This study aimed to identify clinical, neuropsychological and neuroimaging factors that might suggest amyloid neuropathology in patients with clinically suspected AD or aMCI. Methods: Forty patients with mild to moderate AD and 23 patients with aMCI who were clinically diagnosed in our memory clinic and had PiB PET scans were included. Clinical, neuropsychological, and imaging characteristics, such as Medial Temporal lobe Atrophy (MTA) and White Matter Hyperintensities (WMH) on MRI and metabolic pattern on 18 F-labeled fluorodeoxyglucose (FDG) PET, were compared between patients with PiB positive and negative PET results for AD, aMCI, and all subjects combined, respectively. Results: Compared with PiB positive patients, PiB negative patients had a higher prevalence of hypertension history, better performance on the Mini-Mental State Examination, the Rey Auditory Verbal Learning Test, and the Judgement of Line Orientation, lower score of MTA, and were less likely to have temporoparietal-predominant hypometabolism on FDG PET. Affective symptoms were less common in PiB negative patients diagnosed with AD, and the Animal Fluency Test score was higher in PiB negative patients diagnosed with aMCI. Conclusion: In patients with clinically diagnosed AD or aMCI, absence of a history of hypertension, deficits in verbal learning and memory, visuospatial function, semantic verbal fluency, presence of affective symptoms, MTA on MRI, and temporoparietal hypometabolism on FDG PET suggested amyloid deposition in the brain.