Neurocognitive Changes in High-Altitude U-2 Pilots: Relationship between microstructural integrity of white matter tracks and neurocognitive outcomes. (P6.218)

OBJECTIVE: To test if fractional anisoptropy (FA) measurements of white matter tracts can account for neurocognitive differences among the United States Air Force U-2 pilots (U2P) population. BACKGROUND: An increased incidence of white matter hyperintensities (WMH) on fluid attenuated inversion recovery (FLAIR) MRI imaging has been demonstrated in U2P and this increase in WMH count has been linked to cognitive decrements in multiple domains of the MicroCog neurocognitive assessment. Among elderly populations, FA - a measure of white matter microstructural integrity - is linked to decrements in cognitive performance not associated with macroscopic measures of white matter disease, such as WMH volume. DESIGN/METHODS: 101 U2P underwent MRI imaging and cognitive assessments (NP) as previously described. WMH count and volume was calculated as was FA in 67 white matter tracts. RESULTS: FA values of the genu of the corpus callosum was significantly associated with differences of Spatial Processing (p=0.00024), after correcting for multiple comparisons. Additionally a linear regression of the total number of tracts below median FA in a given U2P demonstrated significance (p=0.02) with this same cognitive measure. CONCLUSIONS: This study demonstrates a decline in spatial processing in U2P as a function white matter FA in the genu of the corpus callosum as well as cumulative number of regions with decreased FA. Spatial Processing is not a cognitive domain correlated with increased WMH count / volume in this same population. This supports that changes in white matter FA can contribute to neurocognitive deficits not associated with the accumulation of WMH’s alone in a very healthy population. Disclosure: Dr. Willis has nothing to disclose. Dr. Sladky has nothing to disclose. Dr. Tate has nothing to disclose. Dr. Wood has nothing to disclose. Dr. Sherman has nothing to disclose. Dr. Kochunov has nothing to disclose. Dr. McGuire has nothing to disclose.