The usefulness of carotid ultrasonography in identifying direct-type carotid cavernous fistula

Abstract

We report two cases of direct-type carotid cavernous fistula (CCF) which was diagnosed on carotid ultrasonography (CUS). Case1: A 69-year-old woman. She had abrupt onset of diplopia and tinnitus. Head computed tomography and magnetic resonance imaging (MRI) indicated she had right CCF. CUS indicated an increase in end-diastolic velocity (EDV) of the right internal carotid artery (ICA). Pulsatility index (PI) and resistance index (RI) decreased to 0.63 and 0.45, respectively. CCA end-diastolic ratio rose, and this showed the significant laterality of flow between the right and left ICAs. Case2: An 88-year-old woman who complained visual impairment had right exophthalmos, conjunctival injection and bruit around right orbit. Head MRI demonstrated the dilatation of right superior ophthalmic vein, which reflected the existence of right CCF. On the CUS study, peak systolic velocity (PSV) and EDV of the right ICA were significantly elevated, and PI and RI were decreased to 0.63 and 0.45, respectively. CCA end-diastolic ratio was also significantly elevated. After treatment of the CCF, these values returned toward normal. Since vascular resistance of the affected side is low in CCF patients, CUS easily determined the abnormality as well as the change after treatment. Thus, CUS is useful for both screening and determining the treatment effect of direct-type CCF.Keywords: carotid ultrasonography (CUS)， carotid cavernous fistula (CCF)， pulsatility index (PI)， resistance index (RI)