Magnetic resonance imaging of cerebral compression and local brain tissue water content during continuous extradural bleeding. An experimental study in dogs.

Continuous recording of vital physiologic parameters and magnetic resonance imaging were performed during progressive extradural bleeding in spontaneously ventilated anesthetized dogs. The volume of the bleeding could exceed the intracranial volume by 500 per cent due to the formation of an extradural arteriovenous shunt. The rate of hematoma growth was dependent on the area of stripped dura. Midline shift, herniation and lateral ventricle compression occurred early, corresponding to changes in vital parameters. Local brain water increased non-linearly with white matter preceding gray matter. Water increase started first in the ipsilateral hemisphere followed by the contralateral hemisphere, brain stem and cerebellum. The correlation between local tissue water increase and local perfusion pressure supports the notion of an ischemic brain edema being formed during an extradural bleeding.