Monroe-Kellie doctrine

The Monroe-Kellie doctrine explains that the skull is a fixed space containing three main components: brain tissue, blood, and cerebrospinal fluid. Because the skull doesn’t expand, any increase in one component must be balanced by a decrease in another to maintain normal pressure. If this balance is disrupted—such as from swelling, bleeding, or fluid buildup—it can lead to increased intracranial pressure, which may impair brain function and require medical intervention. Essentially, the doctrine describes the delicate equilibrium within the skull that keeps brain conditions stable.