Middle meningeal artery embolization (MMAE) has emerged as an effective treatment for chronic subdural hematoma (CSDH). Although generally considered safe, rare but potentially devastating visual complications have been reported, most often attributed to embolic migration through angiographically occult anastomoses between the middle meningeal artery (MMA) and the orbital circulation.

A 75-year-old man with recurrent left-sided CSDH underwent MMAE using 12.5% n‑butyl cyanoacrylate (NBCA). Preprocedural angiography revealed a rare vascular anatomy in which the ophthalmic artery originated exclusively from the MMA, with complete absence of internal carotid artery–derived ophthalmic flow. The microcatheter was positioned in a wedged configuration within the MMA during embolization. Immediately after NBCA injection, the patient developed a unilateral superior visual field defect. Postprocedural findings were consistent with embolic diversion into the orbital circulation via angiographically occult meningo-orbital microanastomoses.

This case highlights a rare but clinically important high-risk anatomical and hemodynamic scenario during MMAE. Absence of internal carotid artery–derived ophthalmic flow, together with the use of low-concentration NBCA and local hemodynamic alterations associated with microcatheter wedging, may increase the risk of unintended embolization into occult orbital pathways. Careful preprocedural evaluation of ophthalmic artery origin and individualized embolization strategies are essential, particularly when low-viscosity liquid embolic agents such as low-concentration NBCA are considered.