MR imaging of dural AV fistulas at the cavernous sinus.

The magnetic resonance appearance of dural arteriovenous fistulas (AVFs) at the cavernous sinus (CS) was studied in six angiographically verified cases. Magnetic resonance clearly demonstrated shunted blood as an area of signal void both in the CS and in the superior ophthalmic vein. The relationship between shunted blood, internal carotid artery, and extraocular nerves, as well as proptosis, enlargement of the extraocular muscles, and bulging of the lateral wall of the CS were also depicted in the images. Normal venous flow in the involved CS was shown as a low signal area that enhanced after gadolinium administration. Magnetic resonance is useful for screening and follow-up examinations of dural AVFs at the CS. It is essentially a noninvasive procedure that may be repeated and obviates the need for follow-up angiography. However, it should be noted that a signal void in the CS sometimes represents normal venous flow. A definite diagnosis should rely on angiography, which is essential for therapeutic planning.