In the distal posterior inferior cerebellar artery (PICA), saccular aneurysms originating at the first proximal segment, anterior medullary segment (AMS), are unusual but important due to the presence of critical perforators that branch off the PICA and supply the lower brainstem. Because the anatomy of the PICA varies, no standard treatment strategy has been agreed upon to date. We successfully treated 2 patients with open surgery. One was a 53-year-old man who presented with Hunt-Hess grade 2 subarachnoid hemorrhage (SAH). Cerebral angiography revealed an irregular fusiform AMS aneurysm extending to the lateral medullary segment. Intraoperative inspection showed some perforators to the brain stem branching from just proximal and distal to the aneurysm. The patient underwent aneurysmal trapping and occipital artery-PICA anastomosis to preserve perforators flow, and was discharged without any neurological deficits. Another patient, a 74-year-old woman, was transferred to our institute because she suddenly became comatose. She was found to have a ruptured saccular AMS aneurysm. On the 15th day after the event, she underwent successful aneurysmal clipping preserving perforators by surgical inspection. As both patients manifested intra-aneurysmal thrombosis, we suggest that patients presenting with AMS aneurysms that display unusual features require careful management and judicious choice of treatment. Based on our experience we suggest that direct surgery, which facilitates the identification of perforators and allows for revascularization, is the appropriate treatment choice in patients who present with this entity.