The case reported here, concerns a spontaneous low-flow fistula between the external carotid arterial network and the cavernous sinus, with ophthalmological symptoms (exophthalmos, red eye) in an old woman with cardiac failure. The shunt was diagnosed by color-Doppler-imaging, which showed a flow reversal with a systolic component in the superior and inferior enlarged ophthalmic veins. This finding led the authors to extend the arterial filling sequence since the shunt was not detectable on standard arterial views. Embolization was performed during angiography which remains necessary to localize the shunt and to treat the fistula. The clinical symptoms progressively returned to normal and the correction of the hemodynamic disturbances could be followed by color-Doppler imaging, a non-invasive technique which can be easily repeated.