When a reduction in blood flow lasting seconds occurs, the brain tissue suffers ischemia, or inadequate blood supply. If the interruption of blood flow is not restored in minutes, the tissue suffers infarction followed by tissue death. When the low cerebral blood flow persists for a longer duration, this may develop into an infarction in the border zones (areas of poor blood flow between the major cerebral artery distributions). In more severe instances, global hypoxia-ischemia causes widespread brain injury leading to a severe cognitive sequelae called "hypoxic-ischemic encephalopathy".