Changes in intracranial morphology, regional cerebral water content and vital physiological variables during epidural bleeding. An experimental MR study in dogs.

Epidural bleeding was produced in 8 anaesthetised and heparinised dogs by an artificial system. Changes in vital physiological variables were related to intracranial shifts and tissue water content assessed with MR imaging. Six animals survived while 2 succumbed. In the surviving animals intracranial shifts and compressions remained unchanged from an early stage. The cerebral perfusion pressure was reduced from between 80 and 110 mm Hg to between 40 and 60 mm Hg. Some increase in supratentorial white matter tissue water was observed. In the lethal experiments cerebral perfusion pressure fell to less than 40 mm Hg. Moreover, secondary delayed anatomical changes were seen including hydrocephalus. Increase in cerebral tissue water was more intense and widespread than in the survivors. These findings indicate that the outcome of epidural bleeding is related to cerebral perfusion pressure with secondary deterioration resulting from additional volume loading from increased tissue water and hydrocephalus.