Two cases of distal anterior cerebral artery aneurysm associated with accessory anterior cerebral artery

An accessory anterior cerebral artery (accessory ACA) is a rare anomalous vessel arising from the anterior communicating artery as a median artery of triplicated AGA. It is considered a large median artery of the corpus callosum and distributes to one or both hemispheres. The cases of an accessory AGA aneurysm are extremely rare;, however, we experienced two cases of unruptured aneurysm growing at the distal portion of an accessory AGA. Two females, aged 66 and 67 years, respectively, separately consulted our hospital as a result of chronic headaches. Brain MR angiography and following DSA in the first patient demonstrated a triplicated AGA and an aneurysm located just above the corpus callosum growing from the distal portion of the accessory AGA. MRI and MR angiography in the second patient depicted a triplicated ACA and an aneurysm from the accessory ACA as with the first case. Neck clipping of the aneurysm was performed using an interhemispheric approach in both cases. These aneurysms appeared to present the same intraoperative findings as other unruptured aneurysms growing at the usual positions.