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Figure 13a. Chronic thrombosis of the left transverse and sigmoid sinuses in a 69-year-old man with a chronic headache. (a, b) Axial unenhanced (a) and contrast-enhanced (b) T1-weighted images show an area of the left transverse sinus (arrow) that has isointense signal on a and intensely increased signal on b. The marked contrast enhancement in this case could easily be confused with a normal state of slow flow, which commonly occurs in the left transverse sinus. Venographic techniques therefore were necessary to evaluate sinus patency. (c) Oblique MIP image from coronal TOF MR venography shows an absence of signal in the left transverse sinus, left sigmoid sinus, and left internal jugular vein (arrows) but normal flow in the right transverse sinus, right sigmoid sinus, and right internal jugular vein (arrowheads). (d) Sagittal source image from contrast-enhanced MR venography shows multiple filling defects (arrows) in the recanalized vessels.
