An occlusive device suitable for endovascular treatment of an aneurysm in a region of a parent vessel in a patient, including a structure having a fixed porosity and having dimensions suitable for insertion into vasculature of the patient to reach the region of the aneurysm in the parent vessel. The device further includes a frangible material supported by the structure which initially provides a substantial barrier to flow through the frangible material and is capable of at least one of localized rupturing and localized eroding, in the presence of a pressure differential arising at an ostium of a perforator vessel communicating with the parent vessel, within an acute time period to minimize ischemia downstream of the perforator vessel.
