Reductions in brainstem volume as a key macrostructural indicator in at-risk populations for Alzheimer’s disease

These observations suggest that AD risk, assessed via the presence of MCI or extremely high AD-polygenic risk score is linked to reduced brainstem volume before most typically observed morphological brain alterations. This conforms with evidence implicating the brainstem as one of the earliest sites of morphological neurodegeneration and provides a plausible biological mechanism linking prodromal autonomic symptoms to AD risk in later life. These observations warrant future investigation into the molecular correlates of AD-linked brainstem dysfunction, assessment as a candidate biomarker, and the exploration of brainstem mediated treatment strategies in AD prevention.