Norms for imaging markers of brain reserve.

Brain reserve allows some people to be more resilient to neurodegeneration processes and brain diseases. Structural markers of brain reserve are hippocampus, lateral ventricles, and white matter lesions volume (HV, LVV, WMLV). Subjects in the low end of the distribution of these markers are at higher risk to develop brain diseases such as Alzheimer's disease. We described the distribution of the above markers in a large group of cognitively-intact persons. A sample of 158 people aged between 40 to 90 years (mean ± SD: 60 ± 12 years, education 9 ± 4 years, MMSE score 28 ± 2) belonging to the Italian Brain Normative Archive was selected. HV, LVV, and WMLV were measured with validated procedures. The HV and LVV were measured by manual segmentation and the Freesurfer software, respectively, and normalized by head size; WMLV was measured with semi-automated thresholding. Test-retest reliability was >0.83 for all measures. No relationship was found between HV and age, whereas a significant relationship was found for LVV and WMLV (ventricle left: B 0.02, 95% CI 0.22 to 0.34; ventricle right: B 0.02 95% CI 0.23 to 0.34 p < 0.001; WML: B 0.04; 95% CI 0.03 to 0.06 p < 0.005). The 5th percentile threshold indicating lower brain reserve were: (i) HV below 2,260 mm(3) at 40 and 2,000 mm(3) at 90; (ii) LVV above 17,000 mm(3) at 40 and 60,000 mm(3) at 90; and (iii) WMLV above 1,200 mm(3) at 40 and 8,700 mm(3) at 90. Normative data of brain reserve markers can be used to estimate the brain resilience to neurodegeneration.