Surgical Resection of Idiopathic Distal Anterior Choroidal Artery Aneurysm Assisted by Frameless Stereotactic System Guidance: Case Report and Literature Review. 
Idiopathic distal anterior choroidal artery (AChoA) aneurysms are particularly rare.  Their diagnosis and treatment are difficult because of the particular characteristic of pathological anatomy.  Our case mainly presented with intraventricular hemorrhage.  His idiopathic aneurysm was located in the trigone of the undilated ventricle.  Computed tomographic angiography demonstrated both the precise aneurysm and parent artery even when there was no dilated parent artery for the first time.  It is also the first time this tiny aneurysm was resected assisted by frameless stereotactic guidance during operation after absorption of intraventricular blood.  Computed tomographic angiography and frameless stereotactic guidance benefit the diagnosis and treatment of this kind of aneurysm.  Sacrificing plexual AChoA did not cause any neurologic deficit.