Neuroimaging characteristics of early-onset Alzheimer's disease remain poorly elucidated compared to late-onset forms.

This systematic review examined recent research progress regarding neuroimaging in patients with early-onset Alzheimer's disease (EOAD) and late-onset Alzheimer's disease (LOAD). The population included EOAD patients with various phenotypes, such as non-amnestic variants like logopenic variant of primary progressive aphasia, frontal variant Alzheimer's disease, posterior cortical atrophy, and corticobasal syndrome, alongside LOAD patients. The review focused on structural, functional, and metabolic neuroimaging modalities to characterize disease features.

The primary finding of the review is that the neuroimaging characteristics of EOAD and their differences from those of LOAD remain poorly elucidated to date. Specific numerical data regarding imaging metrics or comparative frequencies were not reported in the source evidence. Consequently, no definitive conclusions can be drawn regarding the efficacy of current imaging protocols for distinguishing these subtypes based on this specific evidence set.

Safety and tolerability data, including adverse events or discontinuations, were not reported for the neuroimaging procedures reviewed. Key limitations explicitly state that the differentiation between EOAD and LOAD imaging profiles is insufficiently defined. The practice relevance of this review is to provide an evidence-based reference for developing EOAD-specific imaging assessment systems and optimizing disease monitoring protocols in future research.

Given the uncertainty and lack of reported quantitative results, clinicians should not rely on this review to establish diagnostic criteria or treatment decisions. Further research is required to clarify the imaging phenotypes of early-onset disease variants.