P3‐239: Asymmetrically Low White Matter Integrity in Seniors with Mci and POOR GAIT Article Swipe

Magnetic resonance diffusion tensor imaging (DTI) allows brain asymmetry to be studied at microscopic scale by examining differences in fiber characteristics across hemispheres. Recent studies demonstrated white matter (WM) asymmetry in healthy older adults exists but its degree is relatively stable during aging and not much dependent on sex. It has been suggested that DTI metrics indicate WM health, maturation, and therefore organization of brain networks shared for cognitive and motor capacity (e.g., gait). As a result, WM disruption may explain the high incidence of falls and predict associated risk in this population. Aberrant asymmetries, reported in several brain disorders, may indicate a pathological progression affecting processes that rely on normal hemispheric specialization. The objective of this study is to evaluate patients diagnosed with Mild Cognitive Impairment (MCI) according to the Petersen criteria for WM asymmetry on DTI and its correlation with gait performance. Twenty four subjects with MCI were evaluated with DTI using a 3T Siemens MRI scanner in addition to comprehensive neuropsychological and neurological evaluation and single- and dual-task gait testing using an electronic walkway (GAITrite systems). Analysis was performed using FSL (Analysis Group, FMRIB, Oxford, UK) and the Tract-Based Spatial Statistics tool, TBSS for left – right differences in common diffusion measures that reflect fiber integrity (fractional anisotropy FA; mean diffusivity, MD). Regions of interest were defined by a registered WM atlas. Significantly decreased FA and increased MD values were observed along WM tracks in the forceps major, left posterior thalamic radiation, corticospinal tract and corpus callosum when compared with the contralateral side within the MCI group. In addition, areas with only significantly decreased FA values and only significantly increased MD values were also detected (e.g hippocampus). Significantly lower WM integrity along the left corticospinal tract correlated with increase dual-task stride time variability and significantly lower WM integrity in the right anterior corona radiata and superior longitudinal fasciculus correlated with increased single-task stride time variability. Significant WM integrity asymmetries were found, allowing further investigations into the correlation between disease state, severity of abnormal WM asymmetry and gait performance in MCI patients.