Monro-Kellie hypothesis

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:

History and etymology

Named after Alexander Monro (1733-1817), a Scottish physician, and George Kellie, a Scottish surgeon (1720–1779).

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rID: 22791
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Cases and figures

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    The skull and its...
    Figure 1: the equilibrium among CSF, blood, and brain tissue
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    The cranial volum...
    Figure 2: the equilibrium among CSF, blood, and brain tissue
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    Liquorice effacem...
    Figure 3: a tumour increasing brain tissue volume
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    Reduced blood vol...
    Figure 4: an increase in CSF volume
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    Venous engorgemen...
    Figure 5: an increase in the blood volume
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