BACKGROUNDDiffusion tensor imaging (DTI) permits quantitative examination within the pyramidal tract (PT) by measuring fractional anisotropy (FA). To the best of our knowledge, the inter-variability measures of FA along the PT remain unexplained. A clear understanding of these reference values would help radiologists and neuroscientists to understand normality as well as to detect early pathophysiologic changes of brain diseases. The aim of our study was to calculate the variability of the FA at eleven anatomical landmarks along the PT and the influences of gender and cerebral hemisphere in these measurements in a sample of young, healthy volunteers.

METHODSA retrospective, cross-sectional study was performed in twenty-three right-handed healthy volunteers who underwent magnetic resonance evaluation of the brain. Mean FA values from eleven anatomical landmarks across the PT (at centrum semiovale, corona radiata, posterior limb of internal capsule (PLIC), mesencephalon, pons, and medulla oblongata) were evaluated using split-plot factorial analysis of variance (ANOVA).

RESULTSWe found a significant interaction effect between anatomical landmark and cerebral hemisphere (F (10, 32) = 4.516, P = 0.001; Wilks' Lambda 0.415, with a large effect size (partial η(2) = 0.585)). The influence of gender and age was non-significant. On average, the midbrain and PLIC FA values were higher than pons and medulla oblongata values; centrum semiovale measurements were higher than those of the corona radiata but lower than PLIC.

CONCLUSIONSThere is a normal variability of FA measurements along PT in healthy individuals, which is influenced by regions of interest location (anatomical landmarks) and cerebral hemisphere. FA measurements should be reported for comparing same-side and same-landmark PT to help avoid comparisons with the contralateral PT; ideally, normative values should exist for a clinically significant age group. A standardized package of selected DTI processing tools would allow DTI processing to be routinely performed in clinical settings.

Adult ; Analysis of Variance ; Anisotropy ; Cerebrum ; metabolism ; Cross-Sectional Studies ; Diffusion Magnetic Resonance Imaging ; methods ; Diffusion Tensor Imaging ; methods ; Female ; Humans ; Male ; Pyramidal Tracts ; metabolism ; Retrospective Studies ; Young Adult