Blindness after middle meningeal artery embolization for skull metastasis of follicular thyroid carcinoma with ophthalmic artery variant.

Background: Preoperative embolization for intracranial tumors is widely used to minimize intraoperative blood loss; however, it carries the risk of ischemic or cranial nerve complications, particularly in patients with anatomical variants. Case Description: A 47-year-old woman with a history of follicular thyroid carcinoma (FTC) was referred after an intracranial mass was detected on magnetic resonance imaging. The lesion was initially suspected to be a meningioma. However, contrast-enhanced computed tomography showed that the tumor was located lateral to the middle meningeal artery (MMA), suggesting an epidural lesion. Angiography confirmed a strong tumor blush from the MMA, and preoperative embolization was performed. During angiography, a branch of the MMA extending toward the orbit was identified; this branch was coil-occluded before Embosphere injection to prevent inadvertent embolization. The patient developed ipsilateral blindness immediately after the procedure. Subsequent internal carotid angiography revealed an anatomical variant in which the ophthalmic artery (OphA) did not originate from the internal carotid artery (ICA). In this context, retinal ischemia was attributed primarily to coil occlusion of the MMA branch supplying the retinal circulation, with possible exacerbation from subsequent Embosphere injection. The tumor was completely resected through craniotomy, and histopathology confirmed metastasis of FTC. At 5 years postoperatively, there was no evidence of intracranial recurrence, although the visual loss was permanent. Conclusion: Skull metastasis of FTC is an uncommon clinical entity. This case highlights a serious complication of preoperative embolization due to a vascular variant in which the OphA was absent from the ICA and the central retinal artery originated from the MMA, leading to irreversible blindness. Thorough angiographic evaluation is essential to identify anatomical variants before embolization. When high-risk anatomy is present, alternative strategies should be considered to minimize the risk of ischemic complications.