Evaluation of intracranial pressure rebound after evacuation of intracranial expanding lesions. An experimental study in dogs.

Sequential magnetic resonance imaging was used to follow brain displacement, signs of herniation and increase in local brain tissue water content during expansion and after evacuation of an extradural balloon in anesthetized, artificially ventilated dogs. A fatal intracranial pressure (ICP) rebound occurred if the cerebral perfusion pressure (CPP) was critically reduced to 20 mm Hg for more than half an hour. Despite reduction of brain displacement after balloon evacuation brain water content continued to increase. Compression of CSF outflow pathways and signs of herniation remained. CPP continuously fell to zero. ICP rebound is a grave situation significantly influenced by a large increase in brain tissue water.