Proximal occlusion for infectious carotid-cavernous fistula caused by invasive fungal sinusitis: illustrative case.

backgroundThirteen cases of fungal cavernous-carotid aneurysms (CCAs) attributable to invasive fungal sinusitis have been reported in the literature. These reports included only 1 case of carotid-cavernous fistula (CCF). In this report, the authors present a case of CCF attributable to the rupture of an infected CCA caused by invasive fungal sinusitis that required proximal occlusion for treatment. OBSERVATIONS: A 56-year-old man with poorly controlled diabetes experienced a sudden loss of vision in his left eye. Cranial imaging revealed invasive sphenoid sinusitis and CCF attributable to a ruptured infected CCA, as well as an unruptured infected supraclinoid internal carotid artery (ICA) aneurysm. After 3 weeks of medical treatment, the patient developed sudden impairment of higher function. MRI revealed occlusion of the distal ICA attributable to thrombosis of the supraclinoid ICA aneurysm. The anterior circulation was perfused from the contralateral side via the anterior communicating artery. Proximal occlusion with coils was performed, leading to ablation of the CCF. LESSONS: This is the first reported case of spontaneous thrombosis of an infected distal cerebral aneurysm, and proximal occlusion with coils was necessary to treat CCF caused by the rupture of a fungal CCA. This case could help guide future treatment. https://thejns.org/doi/10.3171/CASE25336.