Venous Hypertension Associated with a Posterior Fossa Dural Arteriovenous Fistula: Another Cause of Bithalamic Lesions on MR Images

62-year-old man with striking abulia and trouble forming new memories.

A, Axial T2-weighted MR image (3000/108/1 [TR/TE/excitations]) shows increased signal intensity in both thalami (arrow) and evidence of mass effect with convex outer margins of the thalami.

B, Coronal 2D TOF MR venogram shows flow in the internal cerebral veins (solid arrow) but an abnormal appearance of the straight sinus (open arrow).

C, Coronal source image from the venogram shows paradoxical enhancement in both internal cerebral veins (arrow), reflecting flow.

D, Oblique image, sagittal view from the 3D TOF MR angiogram, shows normal basilar artery (short solid arrow), left posterior cerebral artery (open arrow), and deep venous system (long arrow), suggesting arterialized flow in this venous structure.

E and F, Lateral images from a conventional vertebral arteriogram. The arterial phase image (E) shows abnormal early filling of the vein of Galen (curved arrow) and retrograde filling of the internal cerebral vein (straight arrows). On a later image (F), in the capillary phase, opacification of these venous structures is more evident, consistent with an AVF.

G, Follow-up MR image (3000/108/2) 10 months after surgery shows normal appearance of both thalami.