Acupuncture-related brain network findings across clinical stages of the Alzheimer’s disease continuum: a critical review of functional MRI evidence

Brain network abnormalities are observed across the Alzheimer’s disease (AD) continuum, but the relationship between clinical stage, acupuncture-related functional brain changes, and cognitive outcomes remains unclear. This review examined clinical blood oxygen level-dependent functional MRI studies of acupuncture in subjective cognitive decline (SCD), mild cognitive impairment (MCI, including amnestic MCI [aMCI]), and AD dementia. PubMed, Web of Science Core Collection, and China National Knowledge Infrastructure (CNKI) were searched for relevant studies. The evidence was synthesized narratively by clinical stage, with attention to study design, acupuncture protocols, control conditions, imaging methods, brain–cognition associations, biomarker status, and possible cohort overlap. In SCD, the limited available evidence mainly involved changes in regional spontaneous activity, hippocampal connectivity, and network organization. In MCI, including aMCI, reported changes involved memory- and limbic-related regions, DLPFC–ACC connectivity, and locus coeruleus-related pathways. In AD dementia, reported changes mainly involved the hippocampus and posterior medial memory-related regions, with earlier studies mainly examining short-term responses and two longitudinal cohorts assessing changes over a treatment course. Across the reviewed literature, findings in MCI, including aMCI, involved a broader range of brain regions and networks, whereas those in AD dementia were more often centered on the hippocampus and posterior medial memory-related regions. These differences are difficult to attribute to clinical stage alone, given substantial differences across studies in acupuncture protocols, control conditions, imaging methods, sample size, biomarker confirmation, and follow-up. Larger longitudinal studies with biomarker confirmation where possible and complementary imaging modalities are needed to determine whether the observed differences are related to clinical stage and how the imaging changes relate to cognitive outcomes.