Work

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

Year: 2026

Type: article

Abstract: Background Cephalad fluid shift during microgravity may disrupt intracranial fluid homeostasis and contribute to spaceflight-associated neuro-ocular syndrome (SANS). 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 12 h, HDT 1 d, HDT 3 d, HDT 7 d, Recovery (R) 1 d, R 3 d, and R 5 d). 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. Indices reflecting pulsatility and resistance decreased later in 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 remodeling of intracranial dural venous sinus flow and geometry, with early functional changes preceding later caliber changes and a transient impairment in venous-arterial coupling during early recovery. These findings support DVO and DVO/ AI as potential imaging markers relevant to SANS research. Trial registration ChiCTR2500096128 Registration date January 17, 2025

Source: Fluids and Barriers of the CNS

DOI: 10.1186/s12987-026-00845-y