Figure 1 - Evolution of brain blood flow (BBF) in three hypothetical cases of increased intracranial pressure (ICP) with absent supraspinal synaptic activity (coma and absent cephalic reflexes) for at least 48 h prior to cardiac arrest at 60 h-survival. While in case 1 brain damage becomes irreversible within 6 h from the onset of the "brain death" syndrome, in case 2 irreversibility is only achieved within 24 h, and in case 3 the brain tissue is still recoverable by the time of cardiac arrest which may result from metabolic disorders related to hypothalamic failure. If case 1 was representative of all (or at least most) cases of increased ICP at risk of brain death, full maturation of pathological features would develop during the next 48 h of continuous heart beating, and nearly 100% of autopsies (if not all of them) should demonstrate the respirator brain. In contrast, since respirator brain is only seen in 40% of these cases (21), global ischemic penumbra of variable duration is to be alternatively considered. CCtx & BrSt = BBF threshold below which cerebral cortex and brain stem functions become inactive (35 ml 100 g^-1 min^-1); DAMAGE = BBF threshold below which cells depolarize (10-15 ml 100 g^-1 min^-1). HyTh = BBF threshold below which hypothalamic secretory functions become inactive (CCtx & BrSt > HyTh > DAMAGE).