An Eye with a Heartbeat: Carotid Cavernous Fistula-a Case Report

A carotid cavernous fistula is a rare type of arteriovenous (AV) fistula due to an abnormal communication between the cavernous sinus and the carotid arterial system. Normal venous return to the cavernous sinus is impeded as high-pressure arterial blood enters the cavernous sinus. The classical triad of symptoms is characterized by pulsating exophthalmos, ocular bruit, and conjunctival chemosis. However, it is important to note that some patients do not exhibit this triad of symptoms.

A 49-year-old man presented to the Emergency Department (ED) with a chief complaint of "there is a heartbeat in my eye." Pertinent history included an episode of trauma 2 months prior to his onset of unilateral vision loss. Computed tomography scan of the head obtained in the ED upon his initial injury was unrevealing. Despite no identifiable pathology, his pain had gradually worsened since ED discharge. On this occasion, an ocular bruit was appreciated over the affected eye, prompting further diagnostic testing. The patient was admitted for urgent cerebral angiography and definitive endovascular neurosurgical intervention to preserve his eyesight. We discuss the clinical presentation, pathophysiology, and diagnostic modalities important to the management of this rare and potentially devastating cause of vision loss. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: A carotid cavernous fistula is a rare and easily misdiagnosed cause of unilateral ocular pain in the ED. Further, it emphasizes the importance of a detailed clinical history and physical examination to make this diagnosis and save eyesight.