Impaired venous outflow in CVST: prognostic implications of non-functional transverse sinus in a multicentre cohort

BACKGROUND AND OBJECTIVES: Non-functional transverse sinus (NFTS) represents a markedly narrowed but non-thrombosed transverse sinus that may impair cerebral venous outflow. Its influence on the clinical course and outcomes of cerebral venous sinus thrombosis (CVST) remains unclear. This study aimed to evaluate the prevalence and prognostic significance of NFTS among patients with CVST. METHODS: Data from consecutively enrolled patients with confirmed CVST in multicentre databases were retrospectively analysed. NFTS was defined as a transverse sinus showing severe luminal reduction compared with the contralateral side in the absence of thrombosis. Patients with and without NFTS were compared for clinical and radiological features and 90-day excellent functional outcome, defined as a modified Rankin Scale score of 0-1. A preplanned secondary analysis included only patients with unilateral transverse sinus thrombosis sparing the NFTS to isolate its haemodynamic impact. RESULTS: Among 443 CVST patients (mean age 41.4±18.2 years; 64.3% female), 49 (11%) had NFTS. Compared with those without NFTS, affected patients had higher rates of papilledema (50% vs 23%, p<0.001) and multiple cerebral vein involvement (43% vs 22%, p=0.002), with a trend towards lower rates of excellent 90-day outcome (78% vs 87%, p=0.067). In the secondary analysis of 299 patients with unilateral transverse sinus thrombosis not involving NFTS, NFTS (n=29) was associated with more papilledema (51.3% vs 24.3%, p<0.001), multiple vein involvement (51.3% vs 31.9%, p=0.017) and superior sagittal sinus thrombosis (48.7% vs 28.9%, p=0.013). NFTS patients with contralateral transverse sinus thrombosis had poorer outcomes (excellent outcome 74.4% vs 89.7%, p=0.006). NFTS independently predicted non-excellent outcome (OR 4.37; 95% CI 1.5 to 13; p=0.008). CONCLUSIONS: NFTS identifies a subset of CVST patients with impaired venous drainage, greater thrombotic extent, increased papilledema and poorer functional recovery. Recognition of NFTS on baseline imaging may assist in risk stratification and tailored monitoring in CVST.