Relationship between brain tissue pressure gradients and cerebral blood flow distribution studied in circumscribed vasogenic cerebral oedema.

The present experimental study was designed to examine the correlations between brain tissue pressures, pressure gradients and cerebral blood flow distribution associated with circumscribed cerebral vasogenic oedema. Following unilateral hemispheric cryogenic injury in 42 adult cats, brain tissue pressures increased as a function of time. Interhemispheric pressure gradients became most marked one hour after the cryogenic injury (3.9 mm Hg on average), gradually decreasing thereafter. Transtentorial pressure gradients developed within the first hour after the injury, and remained above 10 mm Hg. The dye injected into one carotid system by the "single dye passage" technique was redirected towards the contralateral hemisphere and also towards the subtentorial compartment, as brain tissue pressures increased. The shift in the flow-distribution of dye and blood was more pronounced in the posterior fossa structures. When intracranial tissue pressures exceeded 60 mm Hg almost no dye entered the cranial cavity. This accompanied the marked decrease in cerebral perfusion pressure.