File:The vicious cycle of head injury.jpg

After severe head injury with intracranial pressure (ICP) elevation, a positive feedback loop can ensue, leading ultimately to brain death. This situation can be likened to a compartment syndrome within the noncompliant skull. Elevation of ICP (A) impedes cerebral blood flow (CBF). This leads to ischemia (B, which illustrates an extreme case with strokes in the right anterior and posterior cerebral artery distributions as a consequence of cerebral herniation), which leads to cytotoxic edema caused in part by adenosine triphosphate–dependent Na+-K+ pump failure. This in turn further increases ICP and decreases CBF. This situation can ultimately progress to brain death if ICP becomes so high that the cerebrum is not perfused, as seen on an angiogram.