Changes in the Blood-Brain Barrier After Exposure of the Brain

Prolonged exposure of the brain, such as occurs during neurosurgical procedures, frequently results in cerebral swelling and cerebral edema. These changes are generally attributed to disturbances in the cerebral circulation (Cannon¹; Obrador and Pi-Suñer²; Evans and Scheinker,³ and Prados, Strowger, and Feindel^4,5). Some investigators have been concerned with the permeability of the "blood-brain barrier" in these conditions. By injecting trypan blue intravitally, Prados et al.^4,5 found macroscopically visible staining after exposure of the brain, particularly noticeable in the gray matter of the exposed areas. These experiments showed that cerebral vessels undergo an increase in permeability to trypan blue when the brain is exposed to air. In contrast to these observations, Apfelbach,⁶ Bonvallet and Le Beau,⁷ and Obrador and Pi-Suñer² failed to observe such an increase in trypanblue permeability in their experiments on cerebral edema resulting from exposure or from other experimental procedures.