Diffusion-weighted imaging of intravascular clots in cerebral venous thrombosis

Background and Purpose - Hyperintensities on diffusion-weighted MRI at the site of venous occlusion have previously been reported in cerebral venous thrombosis (CVT). The frequency of these signal changes according to late venous recanalization was not determined yet. Methods - In a series of 28 patients with recent CVT, the frequency of hyperintense signals as seen on diffusion-weighted MRI in vein(s) or sinus(es) (HSVdwi) was assessed at the time of diagnosis, as was rate of recanalization 2 to 3 months after anticoagulation. Results - HSVdwi was detected in 20 occluded vein( s) or sinus( es) in 12 patients (41%) with recent CVT. The mean apparent diffusion coefficient measured in 5 patients within HSVdwi in the superior sagittal sinus was 4.88 +/- 1.49 x 10(-4) mm(2)/s. The delay since clinical onset was larger in the presence than in the absence of HSVdwi as detected at the time of diagnosis. No HSVdwi was visible at the second MRI although some vessels remained occluded. Complete recanalization of the vessel was less frequent when HSVdwi was observed on the first MRI (35% versus 88%, P = 0.005). Conclusions - Results of this study suggest that the movements of water molecules are more or less restricted within the venous clot according to the stage of thrombus formation in CVT. The presence of HSVdwi in occluded veins at the time of diagnosis might be predictive of a low rate of vessel recanalization 2 or 3 months later.