Coil-Assisted Onyx Embolization of an Ophthalmic Artery-Supplied Anterior Cranial Fossa Dural Arteriovenous Fistula Mimicking an Intracranial Aneurysm

Dural arteriovenous fistulas are acquired intracranial vascular malformations characterized by abnormal shunting between dural arterial feeders and venous structures. Anterior cranial fossa and ethmoidal dural arteriovenous fistulas are uncommon but clinically important lesions because they frequently drain directly into cortical veins and may be associated with venous ectasia or aneurysmal venous dilatation. When venous variceal dilatation is present, these lesions may mimic intracranial aneurysms on noninvasive vascular imaging, making digital subtraction angiography essential for definitive diagnosis and treatment planning. We report the case of an 84-year-old man who presented with slurred speech and left-sided limb weakness. Magnetic resonance imaging demonstrated bilateral chronic ischemic white matter changes and lacunar infarct-related signal abnormalities; therefore, the acute presentation was initially attributed to ischemic cerebrovascular disease. However, computed tomography angiography more clearly demonstrated abnormal vessels with localized aneurysm-like dilatation in the right frontal/anterior cranial fossa region, prompting further angiographic evaluation. Digital subtraction angiography revealed an anterior cranial fossa dural arteriovenous fistula supplied by bilateral ophthalmic arteries, predominantly from the right side, with direct cortical venous drainage and aneurysmal venous dilatation in the right frontal region. These findings classified the lesion as a high-grade dural arteriovenous fistula corresponding to Borden type III and Cognard type IV. The patient underwent endovascular treatment under general anesthesia. The dominant right ophthalmic/anterior ethmoidal arterial feeder was selectively catheterized using an Echelon microcatheter over a Synchro microguidewire. Axium Prime detachable coils were deployed in the mid-to-distal arterial segment distal to the origin of the central retinal artery, followed by a controlled injection of Onyx-18. Final angiography demonstrated no residual arteriovenous shunting, complete disconnection of the aneurysmally dilated venous pouch from the arterial feeder, and no early venous filling during the arterial phase. The postoperative course was uneventful, with no clinically evident new neurological or visual complications. This case highlights the diagnostic importance of digital subtraction angiography in aneurysm-mimicking anterior cranial fossa vascular lesions and demonstrates that coil-assisted Onyx embolization may be feasible in carefully selected ophthalmic/anterior ethmoidal artery-supplied dural arteriovenous fistulas when safe distal catheterization and controlled embolic delivery can be achieved.