Figure 11a. Acute thrombus in a 35-year-old woman with a severe headache for 5 days. (a, b) Axial T2-weighted MR image (a) and axial T1-weighted MR image (b) show a thrombus in the left sigmoid sinus (arrows). The signal in the thrombus, compared with that in the normal brain parenchyma, is hypointense in a and iso- to hyperintense in b. (c) Frontal MIP image from coronal TOF MR venography shows a lack of flow in the distal portion of the left transverse sinus and the sigmoid sinus (arrows).