Fig 2. Evolution of acute thrombosis: 43-year-old woman (patient 4) presented for imaging 2 days after onset of severe headache (A–C). Shown are follow-up imaging 197 days later (D–F), axial FSE T2-weighted images (A and D), axial SE T1-weighted images after contrast (B and E), and source images from axially acquired TOF-MRV. On the initial MR (C and F), acute thrombus was identified within the distal transverse and proximal sigmoid sinus. The thrombus was hypointense on T2-weighting (arrows, A) and isointense on T1-weighted images, without enhancement (arrows, B). The thrombosed portions of the sinus exhibited no flow-related signal intensity on TOF-MRV (arrows, C). Some minimal flow signal intensity was seen surrounding the thrombus (arrowhead, C), likely related to collateral flow within dural cavernous spaces or peripherally within the sinus. On the follow-up examination, a central flow void had formed on T2WI and postcontrast T1WI consistent with a recanalized channel (arrows, D and E). Peripheral heterogeneous isointense to hyperintense signal intensity is seen (arrowheads, D), enhancing on postcontrast T1-weighting (arrowheads, E), without flow-related signal intensity on TOF-MRV (arrowheads, F), consistent with enhancing chronic thrombus. The central channel exhibits marked flow-related signal intensity on TOF-MRV (arrow, F).