White matter hyperintensities and hypobaric exposure

Abstract

Objective Demonstrate that occupational exposure to nonhypoxic hypobaria is associated with subcortical white matter hyperintensities (WMHs) on fluid-attenuated inversion recovery magnetic resonance imaging (MRI). Methods Eighty-three altitude chamber personnel (PHY), 105 U-2 pilots (U2P), and 148 age- controlled and health-matched doctorate degree controls (DOC) underwent high-resolution MRI. Subcortical WMH burden was quantified as count and volume of subcortical WMH lesions after transformation of images to the Talairach atlas–based stereo-tactic frame. Results Subcortical WMHs were more prevalent in PHY (volume p = 0.011/count p = 0.019) and U2P (volume p<0.001/count p<0.001) when compared to DOC, whereas PHY were not significantly different than U2P. Interpretation This study provides strong evidence that nonhypoxic hypobaric exposure may induce subcortical WMHs in a young, healthy population lacking other risk factors for WMHs and adds this occupational exposure to other environmentally related potential causes of WMHs.

Reproducibility of quantitative structural and physiological MRI measurements

“…However, these conditions are unlikely to be maintained throughout the life of longer longitudinal or cross‐sectional studies where scanner upgrades, significant hardware changes such as changes head coil, and other methodological changes may be expected. To address these aspects of longitudinal studies, our group and others used two strategies to accommodate for methodological changes: collections of calibration data and use of meta‐ and mega‐analyses (Jahanshad et al., 2013; Kochunov et al., 2015; McGuire et al., 2014a). In the first approach, calibration data are collected before and after change to derive cross‐calibration parameters.…”

“…Twenty‐five (20 males/5 females, average age 25.8 ± 6.4 range 18–41 years) healthy subjects without hypertension, hyperlipidemia, or diabetes meeting USAF Flying Class III neurological standards were recruited (McGuire et al., 2014a,b). All subjects were in a military training environment with a consistently maintained meal time, sleep/wake time, and exercise program.…”

“…Three‐dimensional FLAIR was utilized for analysis of white matter hyperintensities (WMH) as previously described (McGuire et al., 2014a,b). Briefly, FLAIR images were oriented to a common Talairach atlas‐based stereotactic frame using a nine‐parameter affine spatial transformation to ensure consistency of orientation for identification of the periependymal and subcortical regions (McGuire et al., 2013).…”

Cortical Thickness of Native Tibetans in the Qinghai-Tibetan Plateau

“…Acute mountain sickness scores were higher, 34 and visual sensitivities were lower 35 in hypobaric than in normobaric hypoxia. Studies on U-2 pilots showed that hypobaria was associated with a change of white matter hyperintensity 14,36 and with the reduction of cortical thickness. 15 Moreover, exposure to hypobaria after traumatic brain injury worsened brain function.…”

“…11,12 Hypobaria at a HA could also be a factor contributing to brain lesions because it has been proved to induce white matter and cortical thickness impairment. [13][14][15] Environmental ultraviolet rays can cause neuronal damage in the visual system and brain. [16][17][18] Therefore, these HA environmental factors together could have exerted their effect on brain development.…”