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Background <p>Cephalad fluid shift during microgravity may disrupt intracranial fluid homeostasis. However, longitudinal quantitative data characterizing intracranial dural venous sinus adaptation to these fluid shifts remain limited.</p> Methods <p>We conducted a prospective cohort study of 38 healthy adult men undergoing 7-day −6° head-down tilt (HDT) followed by 5-day recovery. 4D flow MRI was acquired at eight time points (Baseline, HDT 12h, HDT 1d, HDT 3d, HDT 7d, Recovery (R) 1d, R 3d, and R 5d). Hemodynamic and morphometric metrics were quantified in the superior sagittal sinus and the transverse sinuses. Time effects were tested using repeated-measures ANOVA or Friedman tests with post-hoc comparisons corrected for multiple testing. Linear mixed-effects models evaluated associations between dural venous outflow rate (DVO) and baseline physiological and biochemical variables within HDT and recovery phases.</p> Results <p>Venous sinuses hemodynamics and morphology changed significantly over time. Mean blood flow rate in both the superior sagittal sinus and representative transverse sinus decreased by HDT 3d and remained below baseline into recovery, while mean cross-sectional area of aforementioned sinuses showed significant reductions most clearly by HDT 7d. Waveform-derived PI and RI decreased later during HDT and persisted into recovery. DVO declined significantly by HDT 3d and remained reduced at R 1d. Arterial inflow rate (AI) progressively declined during HDT and rebounded rapidly at the onset of recovery. DVO/AI was significantly reduced at R 1d and increased by R 5d. Inter-sinus relative pressure difference showed no significant time effect. Baseline renin (<i>β</i> = 0.013, 95% CI: 0.002 to 0.024; <i>P</i> = 0.022) and sodium (<i>β</i> = 0.240, 95% CI: 0.040 to 0.440; <i>P</i> = 0.019) were positively associated with DVO during HDT, whereas baseline cortisol was negatively associated with DVO during recovery (<i>β </i>= −0.084, 95% CI: −0.150 to − 0.017; <i>P</i> = 0.014).</p> Conclusions <p>Short-term −6° HDT induces time-dependent hemodynamic and morphometric adaptations of the intracranial dural venous sinuses, with early functional changes preceding later caliber changes and a transient reduction in the DVO/AI during early recovery. These findings suggest that DVO and DVO/AI may help characterize venous sinus hemodynamic adaptation and venous-arterial flow balance during HDT and recovery.</p> Trial registration <p>ChiCTR2500096128; Registration date: January 17, 2025.</p>

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Hemodynamic and morphologic adaptations of the dural venous sinus to 7-day −6° head-down tilt and recovery: an eight-timepoint 4D flow MRI longitudinal study

  • 期刊论文

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  • 发表日期：

    2026年7月24日

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  • Zhanxin Wu,
  • Huanran Hou,
  • Yan Huang,
  • Furen Guo,
  • Suqin Huang,
  • Yawen Liu,
  • Rui Wang,
  • Jumatay Biekan,
  • Pengfei Zhao,
  • Pengling Ren,
  • Zhenchang Wang

摘要

Background

Cephalad fluid shift during microgravity may disrupt intracranial fluid homeostasis. However, longitudinal quantitative data characterizing intracranial dural venous sinus adaptation to these fluid shifts remain limited.

Methods

We conducted a prospective cohort study of 38 healthy adult men undergoing 7-day −6° head-down tilt (HDT) followed by 5-day recovery. 4D flow MRI was acquired at eight time points (Baseline, HDT 12h, HDT 1d, HDT 3d, HDT 7d, Recovery (R) 1d, R 3d, and R 5d). Hemodynamic and morphometric metrics were quantified in the superior sagittal sinus and the transverse sinuses. Time effects were tested using repeated-measures ANOVA or Friedman tests with post-hoc comparisons corrected for multiple testing. Linear mixed-effects models evaluated associations between dural venous outflow rate (DVO) and baseline physiological and biochemical variables within HDT and recovery phases.

Results

Venous sinuses hemodynamics and morphology changed significantly over time. Mean blood flow rate in both the superior sagittal sinus and representative transverse sinus decreased by HDT 3d and remained below baseline into recovery, while mean cross-sectional area of aforementioned sinuses showed significant reductions most clearly by HDT 7d. Waveform-derived PI and RI decreased later during HDT and persisted into recovery. DVO declined significantly by HDT 3d and remained reduced at R 1d. Arterial inflow rate (AI) progressively declined during HDT and rebounded rapidly at the onset of recovery. DVO/AI was significantly reduced at R 1d and increased by R 5d. Inter-sinus relative pressure difference showed no significant time effect. Baseline renin (β = 0.013, 95% CI: 0.002 to 0.024; P = 0.022) and sodium (β = 0.240, 95% CI: 0.040 to 0.440; P = 0.019) were positively associated with DVO during HDT, whereas baseline cortisol was negatively associated with DVO during recovery (β = −0.084, 95% CI: −0.150 to − 0.017; P = 0.014).

Conclusions

Short-term −6° HDT induces time-dependent hemodynamic and morphometric adaptations of the intracranial dural venous sinuses, with early functional changes preceding later caliber changes and a transient reduction in the DVO/AI during early recovery. These findings suggest that DVO and DVO/AI may help characterize venous sinus hemodynamic adaptation and venous-arterial flow balance during HDT and recovery.

Trial registration

ChiCTR2500096128; Registration date: January 17, 2025.