Spontaneous Carotid-Cavernous Sinus Fistula in an Aged Rhesus Monkey (Macaco, mulatta)

A 35-year-old female rhesus macaque (Macaco mulatta) was examined because of edema and erythema of the right eyelid and injected scieral vessels. Clinical signs progressed to severe chemosis, engorged conjunctival vessels, and exophthalmos with decreased ocular motility and high intraocular pressure. Microbial culturing, examination of conjunctival scrapings, radiography, and analysis of blood samples yielded nondiagnostic results, and palliative treatment was unsuccessful. The discovery of a pronounced bruit near the right eyebrow led to the clinical diagnosis of carotid-cavernous sinus fistula. Confirmation of the diagnosis was made by using orbital ultrasonography, which revealed a dilated superior ophthalmic vein and large extraocular muscles. The research status of the macaque precluded the use of angiography for further diagnostic evaluation or treatment. The macaque was placed on a topically administered beta blocker and observed. The bruit and clinical signs resolved during the ensuing month. There was loss of vision and optic atrophy from glaucoma secondary to the fistula. We believe this was the first reported case of a spontaneous carotid-cavernous sinus fistula in a nonhuman primate.