The Development of Indirect Carotid Cavernous Fistulas after Microvascular Ischemic 4th Nerve Palsies

An indirect carotid cavernous fistula (CCF) is an abnormal connection between the cavernous sinus and internal or external carotid artery. Indirect CCFs often occur spontaneously, particularly in the setting of vascular risk factors such as hypertension, diabetes, and atherosclerosis. Microvascular ischemic nerve palsies (NPs) share these vascular risk factors. However, to date, no temporal relationship between microvascular ischemic NP and indirect CCF occurring sequentially has been reported. We describe the cases of 64- and 73-year-old women who developed indirect CCFs within 1–2 weeks after spontaneous resolution of a microvascular ischemic 4th NP. Both patients had complete resolution and an asymptomatic period between the 4th NP and CCF. This case highlights the shared pathophysiology and risk factors between microvascular ischemic NPs and CCFs, and emphasizes that CCFs should be kept in the differential diagnosis for red eye or recurrent diplopia in patients with previous microvascular ischemic NP.