The Monro-Kellie Doctrine: A Review and Call for Revision

Area of Science:

• Neuroscience
• Physiology
• Biomechanics

Background:

• The Monro-Kellie doctrine is a fundamental concept in intracranial dynamics, positing a fixed cranial volume.
• It explains how changes in intracranial blood, cerebrospinal fluid (CSF), or brain tissue volume are compensated by reciprocal volume shifts to maintain stable intracranial pressure (ICP).
• The doctrine's traditional model assumes an unyielding cranial vault.

Purpose of the Study:

• To review current understanding of calvarial adaptability in response to altered intracranial pressure.
• To propose an updated model of intracranial dynamics that incorporates skull plasticity.

Main Methods:

• Literature review of studies investigating calvarial changes under pathological ICP conditions.
• Synthesis of findings on skull growth and expansion in response to intracranial pressure dysregulation.

Main Results:

• Evidence suggests the calvaria is not rigid and can expand in response to sustained increases in intracranial pressure.
• This adaptability represents a significant compensatory mechanism previously unaccounted for in the Monro-Kellie doctrine.
• Pathological conditions can induce calvarial remodeling and growth.

Conclusions:

• The Monro-Kellie doctrine requires revision to acknowledge the dynamic and adaptable nature of the skull.
• An adaptable calvarium should be considered a fourth component in models of intracranial volume-pressure regulation.
• Integrating skull plasticity offers a more comprehensive understanding of intracranial hemodynamics and pressure management.