A saccular-like dissecting aneurysm of the anterior cerebral artery that developed 2 years after an ischemic event.

Background: A rare case of a growing dissecting aneurysm, which was located at the horizontal (A1) segment of the anterior cerebral artery (ACA), is reported.

Case Description: A 53-year-old woman experienced left hemiparesis and alien hand syndrome. A computerized tomography scan showed an infarction in the right frontal lobe, and cerebral angiography revealed a false lumen and intimal flap at the A1 segment of the ACA. Magnetic resonance angiography demonstrated that the stenosis progressed 6 months later and improved 1 year later. Cerebral angiography showed a saccular-like aneurysm 2 years later. The surgery was planned for prevention of aneurysmal rupture. The aneurysm, which was cocoon shaped, was exposed surgically and was resected. Histological examination of the aneurysm showed arterial dissection. The postoperative course was uneventful without additional neurological deficits.

Conclusion: This is the first case report of A1 dissecting aneurysm presenting with an ischemic event in the literature. The sequential change of the configuration was curious to develop aneurysmal dilatation in 2 years. Long-term follow-up is necessary even after disappearance of the arterial dissection.