Carotid Cavernous Sinus Fistula with Contralateral Feed Not Diagnosed by Virtual Assessment or by Non-Invasive Vascular Imaging.

A 67-year-old woman had delayed initial diagnosis of her right low flow carotid cavernous fistula (CCF) during the coronavirus disease (COVID-19) pandemic due to difficulty detecting ocular signs via online virtual examinations. Her right eye conjunctival erythema and proptosis with medial rectus enlargement on computed tomography scan was initially misdiagnosed as euthyroid thyroid-associated orbitopathy without lid retraction. She developed vision loss, and increasing episcleral venous congestion and CCF was suspected. Computed tomographic angiography did not show an obvious fistula. Digital subtraction angiography revealed the right-sided low flow CCF, which was fed from vessels from the contralateral side.