視野障害で発症し急性期に重度の視力低下に至った破裂前交通動脈瘤の1例

A Case of Ruptured Anterior Communicating Artery Aneurysm with Visual Field Defects and Deteriorating to Severe Vision Loss

われわれは前交通動脈瘤破裂により視神経障害を呈し，治療後に増悪した症例を経験し，特徴的なMRI所見を得たので病態の考察を交えて報告する。症例は47歳男性。右単眼視で上方の視野欠損を認めた。頭部CTでくも膜下出血があり，3D-CT angiographyでは前交通動脈瘤を認めた。脳動脈瘤コイル塞栓術が施行されたが，術後右目は光覚弁に増悪した。術後7日目のMRIでは視神経に接する動脈瘤と視神経の腫脹が確認できた。経過と画像所見より動脈瘤破裂に伴う視神経損傷とその後の脳血管攣縮および動脈瘤による視神経の圧迫が混在し，Ischemic Optic Neuropathy（ION）を呈して重度の視力障害を生じたと考えられた。発症時に視力・視野障害を認める症例ではMRIによる視神経の評価をすみやかに行う必要がある。

Abstract

Although Terson's syndrome is a well-known cause of vision loss due to intracerebral aneurysm rupture, optic nerve neuropathy can also occur because of other causes. Here, we report such a case, i.e., a ruptured anterior communicating artery aneurysm accompanied by vision loss and visual field disturbances due to a cause other than Terson's syndrome. A 47-year-old man presented with right superior altitudinal hemianopia. Computed tomography (CT) showed subarachnoid hemorrhage (SAH), and three-dimensional CT angiography revealed an anterior communicating artery aneurysm. Coil embolization was performed. Right visual acuity degenerated to blindness in the acute stage. MRI performed on day 7 post-admission revealed that the aneurysm had swollen and made contact with the right optic disk. On the basis of the patient's clinical course, we believe that the deterioration in his visual acuity could have been due to ischemic optic neuropathy (ION) resulting from SAH, and the subsequent edema and poor blood perfusion may be attributed to spasm. In cases of visual disturbance associated with SAH, as in our case, it is important to perform MRI to evaluate the damage or risk to the optic nerve as soon as possible.

(Received December 26, 2016; Accepted June 9, 2017; Published October 1, 2017)