To investigate the characteristics of the thrombus at different time points after thrombosis of the intracranial venous sinus, we have developed a new reversible superior sagittal sinus (SSS) model in rats. in this new model, thrombosis was induced by slow injections of the thrombogenic agent into the SSS using a microcatheter. The success of SSS thrombosis was confirmed by magnetic resonance images (MRI), magnetic resonance venographs (MRV), and electron microscopy. T2-weighted MRI and MRV were performed every week for 4 weeks to investigate the process of SSS occlusion. We also examined thrombus formation and the surrounding tissue pathology, as well as endothelial cell injury following SSS occlusion. SSS occlusion occurred at the beginning of the injection of the partial thromboplastin time reagent, and the occluded SSS reopened at the beginning of the second week. MRI images revealed that T2 signals were detected in the parieto- occipital lobes 24 h after SSS thrombosis and disappeared at the end of week two. During week two, the rate of thrombus organization was evident and increased significantly in week three. Thrombus calcification was detected in week three and increased significantly in week four. Electron microscopy examination showed the damaged endothelial cell detected at week three following SSS thrombosis. All of these findings suggest that this reversible SSS thrombosis model is feasible and reproducible. The occlusion state can be maintained for at least 4 weeks, providing an opportunity to study the mechanisms of SSS thrombosis. (c) 2007 Elsevier B.V. All rights reserved.