Incidental findings on brain MRI of cognitively normal first-degree descendants of patients with Alzheimer's disease: a cross-sectional analysis from the ALFA (Alzheimer and Families) project

Objectives: To describe the prevalence of brain MRI incidental findings (IF) in a cohort of cognitively normal first-degree descendants of patients with Alzheimer's disease (AD). Design: Cross-sectional observational study. Setting: All scans were obtained with a 3.0 T scanner. Scans were evaluated by a single neuroradiologist and IF recorded and categorised. The presence of white matter hyperintensities (WMH) was determined with the Fazekas scale and reported as relevant if ≥2. Participants: 575 participants (45-75 years) underwent high-resolution structural brain MRI. Participants were cognitively normal and scored over the respective cut-off values in all the following neuropsychological tests: Mini-Mental State Examination (≥26), Memory Impairment Screen (≥6), Time Orientation Subtest of the Barcelona Test II (≥68), verbal semantic fluency (naming animals ≥12). Clinical Dementia Rating (CDR) had to be 0. Results: 155 participants (27.0%) presented with at least one IF. Relevant WMH were present in 7.8% of the participants, and vascular abnormalities, cyst and brain volume loss in 10.7%, 3.1% and 6.9% of the study volunteers, respectively. Neoplastic brain findings were found in 2.4% of participants and within these, meningiomas were the most common (1.7%) and more frequently found in women. A positive correlation between increasing age and the presence of IF was found. Additionally, brain atrophy greater than that expected by age was significantly more prevalent in participants without a parental history of AD. Conclusions: Brain MRIs of healthy middle-aged participants show a relatively high prevalence of IF even when study participants have been screened for subtle cognitive alterations. Most of our participants are first-degree descendants of patients with AD, and therefore these results are of special relevance for novel imaging studies in the context of AD prevention in cognitively healthy middle-aged participants.