Giant Partially Thrombosed Ophthalmic Segment Internal Carotid Artery Aneurysm With Severe Angiographic–Radiological Discordance: Implications for Microsurgical Strategy

Abstract Background Giant partially thrombosed aneurysms of the ophthalmic segment of the internal carotid artery (ICA) present substantial diagnostic and therapeutic challenges because intraluminal thrombus and mural calcification can obscure the true aneurysm morphology, leading to underestimation of lesion size on angiography. Methods A 53-year-old man with progressive headache without focal neurological deficits or objective visual impairment underwent multimodal imaging including CT, MRI, CTA, and DSA. The imaging findings were integrated for operative planning, and microsurgical clipping with staged thrombectomy was performed. Results CT and MRI revealed a giant partially thrombosed ophthalmic segment ICA aneurysm compressing the optic apparatus, whereas DSA depicted only a small residual lumen, demonstrating marked angiographic–radiological discordance. Microsurgical clip reconstruction with staged intraluminal thrombectomy achieved complete aneurysm exclusion with preservation of the parent ICA and ophthalmic artery. The patient recovered without new neurological deficits and remained functionally independent at 6-month follow-up. Conclusions Giant partially thrombosed ophthalmic segment ICA aneurysms may be substantially underestimated by DSA alone. Integration of CT, MRI, CTA, and DSA is critical for defining true aneurysm morphology and optimizing skull base microsurgical strategy. Microsurgical reconstruction with staged thrombectomy remains a definitive treatment option in selected patients.