Methods

The subjects of this study were normal volunteers who were scanned at Città di Brescia Hospital, Brescia, San Raffaele Hospital, Milan, and Ospedale Borgo Trento, Verona from March 2001 to March 2003. Inclusion criteria were: (1) age greater than 40 years and (2) normal MRI brain as determined by an experience neurologist. Exclusion criteria were based on clinical (before MR scan) and radiological findings (after MR scan). Clinical exclusion criteria were: (1) MR scan for memory problems or cognitive impairment, (2) MR scan for clinical suspicion of neuro-degenerative diseases (Parkinson’s disease, progressive supranuclear palsy, Huntington’s disease, and multiple system atrophy), (3) history of TIA or stroke, head trauma, substance abuse, cortico-steroid therapy, and (4) loss of weight greater than 5 kilograms in the last 6 months.

Radiological exclusion criteria included any MRI scans with: (1) brain mass, (2) white matter hyperintensities in a subject undergoing MR for suspected multiple sclerosis, (3) stroke in a subject with clinical suspicion of recent stroke, (4) aneurisma greater than 10mm, (5) arteriovenous malformation (except for venous angioma), and (6) dysplasia of the central nervous system.

Subjects who gave informed consent to participate to the study underwent a multidimensional assessment including clinical, neurological, and neuropsycological evaluation, and apoE genotyping.

Among the 270 enrolled subjects 5 were excluded for alcohol abuse, 25 for cisterna magna, 3 for stroke, 1 for meningioma, 2 for severe cerebrovascular disease, 1 for extrapyramidal disease, 1 for bipallidal infarction, 1 for amyotrophic lateral sclerosis, 1 for brain atrophy with cognitive impairment resulting from neuropsychological examination, 1 for head trauma, and 2 for missing clinical data.

Magnetic resonance imaging was performed on a 1.5 tesla Siemens Vision (SV) in Milano, 1.0 tesla Siemens Impact (SI) in Verona, and 1.0 tesla Philips Gyroscan (PG) in Brescia.