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Intracranial pressure

Created: 19/12/2006
Updated: 6/8/2021

Intracranial pressure (ICP)

ICP depends on the volume of the intracranial contents: normally 1.4 kg brain, 50-70 ml blood and 50-120 ml CSF.

Normal ICP is 7-17 mmHg (1-2kPa)

Monro-Kellie doctrine

In 1783 Alexander Monro deduced that the cranium was a "rigid box" filled with a "nearly incompressible brain" and that its total volume tends to remain constant. The doctrine states that any increase in the volume of the cranial contents (e.g. brain, blood or cerebrospinal fluid), will elevate intracranial pressure. Further, if one of these three elements increase in volume, it must occur at the expense of volume of the other two elements. In 1824 George Kellie confirmed many of Monro's early observations.

Alexander Monro
Scottish physician, born 22 May 1733, Edinburgh; died 2 October 1817, Edinburgh.

George Kellie
Scottish physician, born 23 April 1758, Whitekirk; died 28 September 1829.

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