Fig. 1

Brain autoregulation (pressure regulation) curve. Cerebral blood flow (CBF) is constant when mean arterial blood pressure (MAP) is kept between 60 and 160 mmHg. As the cerebral vasculature changes to adjust to MAP, vasoconstriction or vasodilatation changes. In patients who had hypertension or severe traumatic brain injury (TBI), the autoregulation curve shifts to the right. Due to the rightward shift (arrow), a MAP-dependent CBF reduction (brain ischemia) or increase (hyperemia) occurs even for a small change in blood pressure. Note that the plateau range of CBF is presumably altered after TBI occurs. No clear data are available, however, on how this presumed alteration takes place