Not All Transverse Sinus Stenoses Behave the Same: Distinct Flow Phenotypes on Phase-Contrast MRI

BackgroundTransverse sinus stenosis is usually assessed by its anatomical appearance, although stenoses with similar morphology may not have the same local flow behavior.This study evaluated peak velocity changes across transverse sinus stenoses using phase-contrast magnetic resonance imaging (MRI) and explored whether distinct hemodynamic patterns could be identified. MethodsWe retrospectively reviewed 183 consecutive patients who underwent brain MRI, magnetic resonance venography, and venous phase-contrast MRI for headache, vertigo, and/or tinnitus between September 2025 and June 2026.Transverse sinus stenosis was identified in 14 patients, including four with bilateral stenosis, yielding 18 stenotic segments.Peak velocity was measured immediately proximal to the stenosis, at the point of greatest narrowing, and immediately distal to it.Each segment was classified as Jet when intrastenotic velocity exceeded both adjacent measurements, Low-flow when it was lower than both, or Intermediate when neither criterion was met. ResultsThe mean age of the 14 patients was 50.7 ± 10.1 years, 11 (78.6%) were women, and the mean body mass index was 27.4 ± 3.5 kg/m².Headache was present in 10 patients (71.4%), vertigo in five (35.7%), and tinnitus in two (14.3%).Across all stenotic segments, mean peak velocity was 16.97 cm/s before the stenosis, 12.84 cm/s within it, and 14.82 cm/s after it.Seven segments (38.9%) showed a Jet pattern, with mean velocities of 14.26, 18.49, and 11.43 cm/s, respectively.Ten segments (55.6%) showed a Low-flow pattern, with corresponding velocities of 19.00, 8.92, and 18.14 cm/s.One segment (5.6%) had an Intermediate pattern.Five patients (35.7%) had three or more imaging findings suggestive of idiopathic intracranial hypertension. ConclusionsTransverse sinus stenoses showed heterogeneous local flow behavior on phase-contrast MRI.Reduced intrastenotic velocity was more common than the expected acceleration pattern, suggesting that anatomical narrowing does not represent a single hemodynamic entity.These preliminary phenotypes require validation against stenosis morphology, venous manometry, and clinical outcomes before their clinical relevance can be established.