Tracking atrophy progression in familial Alzheimerʹs disease: a serial MRI study

Summary Background Serial MRI scanning of autosomal dominant mutation carriers for Alzheimerʹs disease provides an opportunity to track changes that could predate symptoms or clinical diagnosis of the disease. We used hierarchical modelling to assess how hippocampal and whole-brain volumes change as familial Alzheimerʹs disease progresses from the presymptomatic stage through to diagnosis. Methods Nine mutation carriers had serial clinical assessments and volumetric MRI scans (41 scans: range 3–8 per patient) at different clinical stages (presymptomatic, mild cognitive impairment, or clinical Alzheimerʹs disease). 25 healthy controls had serial scanning (54 scans: range 2–4 per patient) for comparison. We measured whole brain and total hippocampal volumes using semi-automated techniques, and adjusted for total intracranial volume. Hierarchical models were developed to estimate differences in volume and atrophy rate between mutation carriers and controls in relation to when the disease was clinically diagnosed. Findings Mutation carriers had significantly increased hippocampal and whole-brain atrophy rates compared with controls and these differences increased with time. Differences in hippocampal and whole-brain atrophy rates between controls and mutation carriers were evident 5•5 and 3•5 years, respectively, before diagnosis of Alzheimerʹs disease. At a cross-sectional level, differences in mean hippocampal volume between mutation carriers and controls became significant 3 years before clinical diagnosis, whereas differences in mean brain volumes became significant only 1 year before diagnosis. Interpretation Structural changes can be seen on MRI scans that predate the clinical onset of familial Alzheimerʹs disease. Longitudinal measures of atrophy rates can identify differences between mutation carriers and controls 2–3 years earlier than cross-sectional volumetric measures.