The Monro-Kellie Doctrine: A Brief Overview

The Monro-Kellie Doctrine was first described over 2 hundred years ago by Dr. Alexander Monro and Dr. George Kellie. It describes a direct relationship between the contents of the skull and intracranial pressure (Mokri, 2001). According to the Monro-Kelli doctrine, the contents of the skull – i.e. brain parenchyma, blood and cerebrospinal fluid (CSF) – are solid/solid (Amin-Hanjani and Smith, 2022). In adults, the intracranial compartment is protected by the skull, a rigid structure with a relentless internal volume of 1,400–1,700 ml (Amin-Hanjani and Smith, 2022). The brain parenchyma constitutes 80% of this volume, the cerebrospinal fluid – 10%, and the blood volume – 10%.

According to the Monro-Kelli doctrine, any increase in the amount of 1 component necessitates a discount within the remaining components through compensatory mechanisms, a rise in intracranial pressure (ICP), or each (Amin-Hanjani and Smith, 2022). The normal ICP value is 5-15 mmHg; a worth above 20 mmHg requires rapid diagnosis and treatment (Benson, Carr, Cutsforth-Gregory, Johnson & Madhavan, 2022). The essential causes of increased intracranial pressure include intracranial mass, cerebral edema, increased CSF production, decreased CSF absorption, obstructive hydrocephalus, venous outflow obstruction, and idiopathic intracranial hypertension (pseudotumor cerebri) (Amin-Hanjani and Smith, 2022).

The Monro-Kelli Doctrine has been a fundamental principle in neurology/neurosurgery for over 2 hundred years. This is a well-accepted principle describing the connection between intracranial contents and intracranial pressure.

Benson, J. C., Madhavan, A. A., Cutsforth-Gregory, J. K., Johnson, D. R., & Carr, C. M. (2022). The Monro-Kellie Doctrine: A Review and Call for Revision. , 10.3174/ajnr.A7721. Previously published online. https://doi.org/10.3174/ajnr.A7721

Edward, S., Amin-Hanjani, S. (2022). Assessment of management of increased intracranial pressure in adults. https://www.uptodate.com/contents/evaluation-and-management-of-podwyższone-ciskie-wewnątrzczaszkowe-u-dorosych

Mokri, B. (2001). Monro-Kellie hypothesis: application in cerebrospinal fluid volume reduction. , (12), 1746–1748. https://doi.org/10.1212/wnl.56.12.1746