During long-duration spaceflight, astronauts experience headward fluid shifts and expansion of the cerebral perivascular spaces (PVS). A major limitation to our understanding of the changes in brain structure and physiology induced by spaceflight stems from the logistical difficulties of studying astronauts. The current study aimed to determine whether PVS changes also occur on Earth with the spaceflight analog head-down tilt bed rest (HDBR). We examined how the number and morphology of magnetic resonance imaging-visible PVS (MV-PVS) are affected by HDBR with and without elevated carbon dioxide (CO₂). These environments mimic the headward fluid shifts, body unloading, and elevated CO₂ observed aboard the International Space Station. Additionally, we sought to understand how changes in MV-PVS are associated with signs of Spaceflight Associated Neuro-ocular Syndrome (SANS), ocular structural alterations that can occur with spaceflight. Participants were separated into two bed rest campaigns: HDBR (60 days) and HDBR + CO₂ (30 days with elevated ambient CO₂). Both groups completed multiple magnetic resonance image acquisitions before, during, and post-bed rest. We found that at the group level, neither spaceflight analog affected MV-PVS quantity or morphology. However, when taking into account SANS status, persons exhibiting signs of SANS showed little or no MV-PVS changes, whereas their No-SANS counterparts showed MV-PVS morphological changes during the HDBR + CO₂ campaign. These findings highlight spaceflight analogs as models for inducing changes in MV-PVS and implicate MV-PVS dynamic compliance as a mechanism underlying SANS. These findings may lead to countermeasures to mitigate health risks associated with human spaceflight.

在长时间的太空飞行中，宇航员会经历头部液体的移动和脑血管周围空间（PVS）的扩张。我们对太空飞行引起的大脑结构和生理学变化的理解的一个主要限制源于研究宇航员的后勤困难。目前的研究旨在确定太空飞行模拟头朝下倾斜卧床休息 (HDBR) 是否也会在地球上发生 PVS 变化。_{我们研究了在二氧化碳 (CO 2} )升高和不升高的情况下 HDBR 对磁共振成像可见 PVS (MV-PVS) 的数量和形态的影响。这些环境模仿了在国际空间站上观察到的向头流体移动、身体卸载和 CO _2升高。此外，我们试图了解 MV-PVS 的变化如何与太空飞行相关神经眼综合症 (SANS)（太空飞行时可能发生的眼部结构改变）的症状相关。参与者被分为两个卧床休息活动：HDBR（60 天）和 HDBR + CO _{2 （30 天，环境 CO 2}升高）。两组患者在卧床休息前、卧床休息期间和卧床休息后均完成了多次磁共振图像采集。我们发现，在群体水平上，航天类似物都不影响 MV-PVS 数量或形态。然而，当考虑到SANS状态时，表现出SANS迹象的人几乎没有或没有表现出MV-PVS变化，而他们的无SANS对应者在HDBR + CO 2 活动期间表现出MV-PVS形态_变化。这些发现强调了航天模拟作为引起 MV-PVS 变化的模型，并暗示 MV-PVS 动态顺应性是 SANS 的基础机制。这些发现可能会导致采取对策来减轻与载人航天相关的健康风险。