Impact of intracranial hypertension and cerebral perfusion pressure on spreading depolarization

Spreading depolarization (SD) develops after stroke and traumatic brain injury and may contribute to secondary brain damage. These diseases are often accompanied by intracranial hypertension, but little is known about the effects of intracranial pressure (ICP) on SD. Here, we study the effect of increased ICP on hemodynamic and metabolic response to SD in rats. SDs were triggered at different ICPs and cerebral perfusion pressures (CPP). The regional cerebral blood flow (rCBF), partial pressure of brain tissue oxygen (PbtO₂), cerebral extracellular glucose and lactate concentrations were recorded. Fluoro-Jade staining was used to quantify neuronal injury in cortex. At high ICP (50 mmHg) with low CPP (30 mmHg), rCBF and PbtO2 were monophasically decreased in contrast to a monophasically increased pattern under normal conditions. Neuronal death increased in both hemispheres but much more on the side where SDs were triggered. At high ICP (50 mmHg) with normal CPP (70 mmHg), CBF and metabolism during SD did not differ from baseline, and neuronal death did not increase even on the side of SD induction. These data suggest that maintaining CPP at 70 mmHg, even when the ICP is as high as 50 mmHg, preserves normal blood flow and metabolism during SD events and prevents neuronal degeneration.