Background: In human beings exposed to high altitude, cerebral magnetic resonance imaging (cMRI) revealed alterations ranging from subclinical cerebral edema formation to subtle brain abnormalities. Yet, brain structure after adaptation to high altitude and their recovery after return to lowlands have been rarely investigated. We, therefore, examined 10 healthy individuals by cMRI before, 12 hours after descent (R + 12h), and again 3.5 months (R + 3.5m) after a 7-day high altitude exposure at 4554 m. Results: After their 3-day lasting, stepwise ascent to 4554 m, all subjects suffered acute mountain sickness with a mean Lake Louise score of 5.8 ± 1.7 after the first night at that altitude. Acute mountain sickness completely resolved after 4 days at 4554 m. While 12 hours after descent mean white and gray matter volumes were increased compared with before altitude exposure (p = 0.045 and p = 0.002), these volumes were normalized on R + 3.5m. Moreover, we observed significant focal volume alterations likely attributed to either vasogenic or cytotoxic edema formation. Two subjects presented new brain findings after altitude exposure. In one individual the number of preexisting white matter hyperintensities (WMHI) transiently increased, in the other individual a reversible splenial lesion syndrome (RESLES) emerged. Both findings had resolved 15 and 8 days after descent, respectively. None developed structural lesions like brain atrophy, cerebral infarcts, microbleeds, or high-altitude cerebral edema. Discussion: Three days after complete recovery from acute mountain sickness and after return to low altitude, subclinical vasogenic and cytotoxic edema, RESLES and WMHI are present in high-altitude acclimatized individuals. However, these cerebral alterations are reversible within months at lowland.

中文翻译：

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在4554 m下经过7天的观察性脑磁共振成像研究。

背景：在暴露于高海拔地区的人类中，脑磁共振成像（cMRI）显示出从亚临床脑水肿形成到微妙的脑部异常的变化。然而，很少研究适应高海拔后的大脑结构以及返回低地后的大脑结构。因此，我们在下降后12小时（R + 12h）以及在4554 m处进行7天高空暴露后3.5个月（R + 3.5m）进行了cMRI检查，对10名健康个体进行了检查。结果：在持续3天的逐步上升至4554 m后，所有受试者在该海拔高度的第一晚之后均患有急性高山病，平均路易斯湖评分为5.8±1.7。在4554 m下经过4天后，急性高山病完全消失。与下降前相比，下降后12小时的平均白和灰质体积增加（p = 0.045和p = 0.002），这些体积在R + 3.5m上归一化。此外，我们观察到明显的病灶体积改变可能归因于血管生成或细胞毒性水肿的形成。两名受试者在高度接触后出现了新的大脑发现。在一个个体中，先前存在的白质高信号（WMHI）的数量短暂增加，在另一个个体中，出现了可逆性脾损伤综合征（RESLES）。下降后第15天和第8天，这两个发现均得到解决。没有人出现结构性病变，如脑萎缩，脑梗塞，微出血或高海拔脑水肿。讨论：从急性高山病完全恢复并返回低空后三天，在高度适应环境的人群中出现亚临床血管生成和细胞毒性水肿，RESLES和WMHI。然而，在低地，这些脑部改变在数月之内是可逆的。