Monro-Kellie hypothesis is a pressure-volume relationship that aims to keep a dynamic equilibrium among the essential non-compressible components inside the rigid compartment of the skull 1-3.
The average intracranial volume in the adult is around 1700 mL, composed of brain tissue (~1400 mL), CSF (~150 mL), and blood (~150 mL) 3,4. The volume of these three components remains nearly constant in a state of dynamic equilibrium (Figures 1 and 2). Thus, a decrease in one component should be compensated by the increase in other and vice-a-versa (Figures 3, 4 and 5).
It is important to note that most of the blood in the cranial cavity is contained in the low-pressure venous system, so venous compression serves as a means of displacing blood volume 2.
There are many classic brain imaging findings that this theoretical hypothesis can explain:
- venous distention in intracranial hypotension
- sulcal effacement in brain oedema or expansive lesion
- brain shift with intracranial hypertension
- hydrocephalus in idiopathic intracranial hypertension
History and etymology
Named after Alexander Monro (1733-1817), a Scottish physician, and George Kellie, a Scottish surgeon (1720–1779).
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- 2. Hannon RA, Pooler C, Porth CM. Porth Pathophysiology. Lippincott Williams & Wilkins. (2009) ISBN:1605477818. Read it at Google Books - Find it at Amazon
- 3. Hickey JV. Clinical Practice of Neurological and Neurosurgical Nursing. Lippincott Williams & Wilkins. (2011) ISBN:1451161018. Read it at Google Books - Find it at Amazon
- 4. Rangel-Castilla L, Rangel-Castillo L, Gopinath S et-al. Management of intracranial hypertension. Neurol Clin. 2008;26 (2): 521-41, x. doi:10.1016/j.ncl.2008.02.003 - Free text at pubmed - Pubmed citation