一過性の下方視野障害を呈した左内頸動脈眼動脈分岐部動脈瘤の1例  [in Japanese] A Case of Carotid-ophthalmic Aneurysm Cause of a Transient Lower Half Visual Field Defect  [in Japanese]

We report a case of carotid-ophthalmic aneurysm that caused a transient lower half visual field defect. A 41-year-old man experienced a transient lower half visual field defect in his left eye. Computed tomographic angiography (CTA) and digital subtraction angiography (DSA) showed a left carotid-ophthalmic aneurysm 8mm in diameter projecting superiorly. The position of the supraclinoidal portion and the bifurcation of the left internal carotid artery (ICA) were lower than the other side. Neck clipping was performed with a right-angled clip after anterior clinoidectomy and optic canal unroofing. Intraoperative findings showed the aneurysm was located just under the left optic nerve and stretched it superiorly. The upper surface of the optic nerve was compressed at the edge of the falciform ligament. The postoperative course was uneventful. We think the aneurysm displaced the optic nerve superiorly against the falciform ligament and the compression of the upper surface of the optic nerve caused the lower half visual field defect. Direct surgery is adequate treatment in this case to avoid further damaging the visual function because coil embolization may enlarge the aneurysm. The low position of the supraclinoidal portion and the bifurcation of the ICA result in optic nerve compression. This radiographical findings of CTA and DSA are characteristic and may help understanding the symptom.