An occlusive device suitable for endovascular treatment of an aneurysm in aregion of a parentvessel in a patient, including a structure having a fixed porosity and havingdimensions suitablefor insertion into vasculature of the patient to reach the region of theaneurysm in the parentvessel. The device further includes a frangible material supported by thestructure which initiallyprovides a substantial barrier to flow through the frangible material and iscapable of at least oneof localized rupturing and localized eroding, in the presence of a pressuredifferential arising atan ostium of a perforator vessel communicating with the parent vessel, withinan acute timeperiod to minimize ischemia downstream of the perforator vessel.
