Monro-Kellie Doctrine

The Monro-Kellie Doctrine states that the skull is a fixed, rigid space containing three main components: brain tissue, blood, and cerebrospinal fluid (CSF). Since the skull cannot expand, any increase in one component’s volume must be offset by a decrease in another to maintain normal pressure. If this balance is disturbed—such as bleeding or swelling—the pressure inside the skull rises, which can damage the brain. This principle helps explain how the body compensates for changes in brain conditions and guides the management of head injuries and brain diseases.