Dilated intercavernous sinuses: an MR sign of carotid-cavernous and carotid-dural fistulas.

Dilated venous channels traversing the sella and connecting the two cavernous sinuses were seen on contrast-enhanced MR images in four patients with angiographically proved carotid fistulas. The anatomy and variations of these so-called intercavernous sinuses are discussed and are demonstrated in Latex-injected anatomic specimens. Direct visualization of the intercavernous sinuses on contrast-enhanced MR images may serve as an ancillary sign for the diagnosis of carotid-cavernous or carotid-dural fistulas near the sella.