FIG 1. Lateral-projection angiogram of the left common carotid artery shows a direct carotid cavernous fistula, with the ostium in the inferior C4 portion of the ICA just anterior to the posterior genu. Fistulous flow to the cavernous sinus, with effluence to an attenuated superior ophthalmic vein, a single channel connecting to the pterygoid plexus, is present. No inferior petrosal sinus opacified.