Objective: A direct aspiration technique using a 5MAX ACE catheter (Penumbra, Alameda, CA, USA) has been reported. However, recanalization has not been achieved in all cases with this technique alone. Additionally, Japan has a rapidly aging society, and differences in the condition of vessels, because of aging, can limit the approach of revascularization devices to the thrombus. We evaluated the accessibility of the 5MAX ACE (0.060-inch inner diameter) over the clinoid segment of the internal

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... rotid artery (ICA). Methods: We conducted a retrospective and cross-sectional study of 28 patients who received intraarterial treatment for acute ischemic stroke between October 2014 and October 2016. We recorded the maximum distal arrival point of the distal edge of the 5MAX ACE during the procedure before the stent retriever was retrieved. Results: In 5 of the 28 patients, the distal edge of the 5MAX ACE catheter did not advance over the clinoid segment of the ICA. The mean age of patients for whom the 5MAX ACE catheter failed to advance over the clinoid segment of the ICA was significantly higher (non-advancement: 85 ± 3 years) than that of patients with advancement (76 ± 9 years, Mann-Whitney U-test: P = 0.04). Conclusion: Advanced age may limit successful revascularization using only a direct aspiration technique with the 5MAX ACE without a stent or balloon anchoring technique for lesions at the terminal portion of the ICA and more distal arteries, which suggests that different devices or approaches may be needed for clot removal. Keywords▶ 5MAX ACE, high-aged population, accessibility, clinoid segment of the internal carotid artery