To report two patients who, after neurosurgical clipping and embolization due to fistula between a posterior communicating artery aneurysm and the cavernous sinus, experienced aggravation of symptoms encompassing increased proptosis, elevation of intraocular pressure, choroidal effusion, and venous stasis retinopathy.

Carotid cavernous fistula is described as an abnormal conduction between the cavernous sinus and the carotid arterial system. But fistula between a posterior communicating artery aneurysm and the cavernous sinus is very rare and few such cases have been reported in the literature so far. Patients with abnormal communication between the arterial and venous systems within the cavernous sinus in the skull may initially present with decreased vision, conjunctival chemosis, external ophthalmoplegia, and proptosis. The conventional treatments for the fistula include carotid ligation and embolization and for posterior communicating artery aneurysms include neurosurgical clipping and coil embolization.

We report two patients including a 51-year-old man and a 43-year-old woman, who were known cases of treated fistula between a posterior communicating artery aneurysm and the cavernous sinus via neurosurgical clipping and embolization, who presented with decreased vision, eye proptosis, conjunctival chemosis and dilated episcleral vessels. Further evaluation demonstrated that the patients had elevated intraocular pressure with a shallow anterior chamber. Fundus examination revealed superficial intraretinal hemorrhagic lesions and choroidal effusion. After cerebral angiographic evaluation, the fistula of the patients was found to have closed successfully. Based on their history and imaging studies including ultrasound bio microscopy, optical coherence tomography, and fluorescein angiography; a diagnosis of secondary choroidal effusion with angle closure glaucoma and venous stasis retinopathy was made, and the patients were treated with full anti-glaucoma medication including eye drops of timolol-dorzolamide, latanoprost and oral medication with acetazolamide. The signs were diminished dramatically after medication and the patients were observed through follow-up visits.

Although neurosurgical clipping and embolization is an effective treatment for fistula between a posterior communicating artery aneurysm and the cavernous sinus, nonetheless, sight-threatening complications can develop after therapy due to progressive ophthalmic vein thrombosis which should be carefully monitored.