Blood-brain barrier permeability in staphylococcal cerebritis and early brain abscess

The pattern of radiographic enhancement in cases of brain abscess has been extensively studied, but the magnitude of blood-brain barrier (BBB) damage that accompanies enhancement has not. The question of whether BBB permeability increases continuously as a cerebritis evolves into an abscess was studied. The tracers 3H-labeled aminoisobutyric acid and 14C-labeled butanol were used in a rat Staphylococcus aureus cerebritis model to measure simultaneously BBB permeability and blood flow. The rats were examined at 1, 2, 3, 5, or 7 days after inoculation, and tissue samples were collected from the cerebritis site and uninoculated regions. Permeability of the BBB in the cerebritis region increased to five times the normal values by 72 hours after inoculation, then reached a plateau. The plasma volume in the cerebritis region increased to six times greater than the normal value at 72 hours, then remained unchanged. Uninoculated brain in both ipsilateral and contralateral hemispheres showed no significant changes. Cerebral blood flow was not substantially altered at the inoculated or uninoculated sites. In this model, incidence of BBB damage rises rapidly, reaches a plateau, and does not continue to increase despite the ongoing evolution of a cerebritis into an abscess. The BBB damage is accompanied by an increase in the regional plasma volume, a novel finding that has not been previously reported in central nervous system inflammation. These results suggest that the vascular events contributing to brain edema formation become established early in the cerebritis phase and imply that control of the host's inflammatory response is important in the management of cerebritis-associated brain edema.