Further topics include a proposal for a major multicenter re-study of the utility of extracranial-intracranial bypass surgery in light of additional diagnostic information available through PET scanning; examination of how processes such as apoptosis, inflammation, free radicals, poly (ADP-ribose) polymerase activation, and alterations in glutamate receptor function contribute to the pathogenesis of ischemic brain injury; and finally an exploration of how estrogens or cholesterol-lowering agents might be used therapeutically.