Fig. 3.

The perfusion window and the cycle that narrows it. a Cerebral blood flow is held constant across the autoregulatory plateau; below the lower limit flow becomes pressure-passive and falls, and above the upper limit pressure breaks through. The dashed curve shows the rightward shift of chronic hypertension, so that pressures normal for others fall below the shifted lower limit. b The self-amplifying cycle of pulsatile injury; each turn stiffens the vessel further, and the cycle exits both into the hypoperfusion arm and, ultimately, into intracerebral hemorrhage