Time course of brain volume changes in the preclinical phase of Alzheimer's disease

Structural alterations of a large network characterize Alzheimer's disease (AD), but the time course of these changes remains unclear. The dynamic of these alterations was examined in the AD preclinical phase using data from the 10-year follow-up of a population-based cohort (Bordeaux-3City).

Participants received neuropsychological assessments every 2 years and two identical magnetic resonance imaging (MRI) exams at baseline and 4 years later. Twenty-five incident AD cases were compared with 319 subjects who remained free of dementia. Subjects were free of dementia at baseline and at follow-up MRI. Incident AD occurred after these time points.

At baseline, incident AD already presented smaller volumes only in the left amygdalo-hippocampal complex. Moreover, a higher annual rate of atrophy of the temporoparietal cortices was observed in future AD subjects during the following 4 years.

Incident AD cases present mediotemporal lesions up to 5 years before diagnosis. This neurodegenerative process seems to progressively reach the temporoparietal cortices in the AD preclinical phase.