Unusual Location of Anterior Communicating Artery Aneurysm Located on the Planum Sphenoidale Due to Long A_1 Segments

A 51-year-old woman presented with a rare variation in the location of the anterior communicating artery (AComA) complex associated with aneurysm manifesting as sudden onset of headache. Computed tomography (CT) revealed widespread subarachnoid hemorrhage with intracerebral hematoma and intraventricular hemorrhage. Three-dimensional (3D)-CT angiography revealed an aneurysm located at the AComA complex on the planum sphenoidale. Surgical clipping of the aneurysm through the right pterional approach was performed without complication. AComA aneurysm located on the planum sphenoidale is extremely rare, but should be recognized in the planning of surgery in the AComA region. 3D-CT angiography is very useful for understanding the relationships between aneurysms and the surrounding structures.