Narrower jugular bulbs and their tributaries are associated with skull base venous hyperintensity on arterial spin-labeling MRI.

Incidental arterial spin-labeling MRI hyperintensity (ASL+) at the jugular bulb (JB) can mimic dural arteriovenous fistula but its anatomical basis remains incompletely understood. We investigated whether JB and tributary sizes are associated with ASL+. We retrospectively analyzed MRIs from 25 ASL+ patients and 25 controls, using post-contrast SPGR images to measure JB and tributary diameters. Group comparisons, effect sizes, false discovery rate (FDR) correction, and receiver operating characteristic (ROC) analyses were performed, with leave-one-out cross-validation (LOOCV) to assess model stability. ASL+ patients demonstrated smaller JB midportion (P = 0.047, Cohen's d = 0.58), JB outflow (P = 0.030, d = 0.63), and posterior condylar vein (PCV) diameters (P = 0.009, d = 1.02). After FDR correction across eight comparisons, only PCV remained statistically significant. ROC analysis demonstrated moderate discrimination for JB measures (AUC ≈ 0.67) and stronger discrimination for PCV (AUC = 0.78). A multivariate model achieved AUC = 0.83 with stable LOOCV performance (AUC = 0.77), suggesting limited overfitting. Thus, we identify a venous morphometric pattern associated with ASL+, characterized by smaller JB and PCV calibers. However, given multiplicity adjustment and spatial-resolution constraints for PCVs, these associations should be interpreted as exploratory. This composite anatomical configuration may contribute to delayed venous transit and ASL signal trapping, providing a plausible structural contributor to this imaging pitfall and informing future mechanistic investigations.