Aim:Treatment of distal internal carotid artery (ICA) and ICA terminus (ICAT) aneurysms using flow-diverting devices (FDD) usually requires deployment of the device from the ICA up to the proximal middle cerebral artery (M1). Only a few studies have examined ischemic complications due to in-stent stenosis (ISS) or in-stent thrombosis (IST) of the middle cerebral artery (MCA) and lenticulostriate arteries after FDD deployment from the ICA to M1. We therefore sought to gain a better understanding of ischemia risk related to this surgical intervention. Material and Methods:Using data from a prospectively maintained database, we retrospectively evaluated patients who were treated with FDD between January 2015 and 2020 at a single academic center. Patients with both ruptured and unruptured ICA aneurysms where the FDD was extented into M1 were included.Results:In total, 129 patients with 138 ICA aneurysms were treated with FDD. A total of 34 patients with 36 aneurysms had FDD extending into M1. Of the 34 patients, six experienced MCA and lenticulostriate territory ischemia (17.6%). Four patients had IST, and two patients had severe ISS. The overall ischemic complication rate was 17.6%, which resulted in permanent neurological deficit in 11.7% of the patients.Conclusion:If the distance of the distal neck of the aneurysm to the ICAT is ≤5 mm or if the aneurysm is located directly at the ICAT, FDD should be considered as the last option when other treatment modalities are not suitable. In addition, in the treatment of distal ICA aneurysms, extra effort should be exerted during the procedure to deploy the FDD without extending into M1. However, when traditional microsurgical clipping and other endovascular procedures are not suitable, the use of FDD is safe in terms of high aneurysm occlusion rates and preventing aneurysm rupture.