The role of deep medullary vein visibility in the relationship between cerebral microbleeds and white matter interstitial fluid

To investigate the relationship between cerebral microbleeds (CMBs) and interstitial fluid (ISF) content in white matter and to statistically assess whether impaired visibility of deep medullary vein (DMV) is associated with this relationship. Clinical and multimodal magnetic resonance imaging (MRI) data were obtained from 150 patients admitted to a neurology department. DMV visibility and integrity were scored (range, 0–18) using susceptibility-weighted imaging (SWI), and the number of CMBs was assessed on SWI magnitude images. The free water (FW) fraction derived from diffusion tensor imaging was used to quantify extracellular ISF content. The mean age of the participants was 61 ± 12 years, and 53 patients (35.3%) exhibited CMBs. The median DMV score was 3 (interquartile range, 1–8), and the mean FW value was 0.25 ± 0.02. Patients with CMBs had significantly higher FW values and DMV scores than those without CMBs. General linear model analysis confirmed an independent association between CMBs and FW values (P < 0.05). Mediation analysis demonstrated that DMV scores statistically partially reflected the association between CMBs and FW values after adjustment for age, sex, and vascular risk factors (P < 0.05). In this cross-sectional exploratory study, CMBs are independently associated with increased ISF content in white matter, and impaired DMV visibility statistically accounts for a portion of this association. These findings reflect statistical relationships only; causal interpretation is not supported by the study design.