Diffusion along the perivascular space influenced by handedness and language lateralisation

The DTI-ALPS_index (diffusion tensor image analysis along the perivascular space index) has been tested in several diseases, but a limited number of studies are available in healthy normal populations. Given that some of the examined diseases show asymmetric features (e.g. Parkinson's disease, epilepsy) and considering that the DTI-ALPS_index is calculated from white matter regions involved in motor and language functions, our aim was to examine whether the index is influenced by handedness and/or functional language lateralisation. Eighty-two Caucasian adults (35 males; mean age: 26.91 ± 10.17, range: 18-66 years) were included in this retrospective cross-sectional study. Handedness was assessed by the Edinburgh Handedness Inventory, while language lateralisation was determined by functional MRI at 3T using a verbal fluency paradigm. The left- and right-hemispheric as well as the bilateral DTI-ALPS indices were calculated independently by two observers. Multiple linear regression corrected for age and sex indicated that handedness was inversely related to the left ALPS_index by Observer1 (n = 81, two-tailed P = 0.030) and the bilateral ALPS_index by both observers (n = 82, P = 0.025 and P = 0.044), but not significantly related to the right ALPS_index. In females, multiple linear regression corrected for age indicated that language laterality index was inversely related to the left ALPS_index (n = 47, P < 0.001) and the bilateral ALPS_index (n = 47, P ≤ 0.003) by both observers, but not significantly associated with the right ALPS_index. In males, language laterality index was not related to any of the ALPS indices. Providing further insights into the normal DTI-ALPS patterns, our study supports the hypothesis that both language laterality and handedness can affect DTI-ALPS index that should be considered in future studies.