前大脳動脈水平部窓形成部に発生した未破裂脳動脈瘤の1例

Unruptured Aneurysm Arising from Fenestration of the Horizontal (A1) Segment in the Anterior Cerebral Artery: A Case Report and Review of the Literature

Ⅰ．はじめに

　椎骨脳底動脈系の窓形成（fenestration）は時に経験される．内頚動脈系に発生した窓形成は前交通動脈にはよく認められるが，前交通動脈以外の窓形成の報告は少ない．今回，われわれは前大脳動脈水平部に発生した無症候性未破裂脳動脈瘤に直達手術を施行した症例を経験したので，文献的考察を加えて報告する．

　Cerebral aneurysms arising from fenestration of the horizontal (A₁) segment in the anterior cerebral artery (ACA) are very rare. In this paper,we report our case,discuss radiological features,and review previous cases. A 70-year-old male was referred to our hospital presenting with memory disturbance. His unruptured cerebral aneurysm in the A₁ segment was incidentally found by magnetic resonance angiography (MRA). Three dimensional computed tomographic angiography (3D-CTA) demonstrated this aneurysm arising from fenestration of the A₁ segment. Surgical neck clipping was performed via the pterional approach,while sacrificing one pair of the A₁ segment. The patient's post operative course was uneventful.

　Only 14 cases with an aneurysm arising from fenestration of the A₁ segment have been reported previously. In the present case,3D-CTA was very useful for finding out where the aneurysm arose from,and we also had to be careful about perforating arteries from the A₁ segment during the surgery.