Describe the physiology of intracranial pressure and the physiological mechanisms that limit a rise in intracranial pressure.

[Click here to toggle visibility of the answers]

College Answer

Candidates who did well in this question used graphs to describe the various 
concepts, described normal physiology and covered the breadth of the topic. A good 
answer made mention of normal values of ICP, it’s variation with respiration and 
blood pressure and illustrated a trace of the ICP. An explanation of the Monroe Kelly 
doctrine was expected, CSF production and absorption and it’s relationship to raised 
ICP as well other compensatory mechanisms for a high ICP (eg displacement of 
CSF into spinal canal, displacement of venous blood into the jugular veins, rise in 
ICP leads to ischaemia if the brain. Critical ischaemia invokes the Cushing reflex.
Major omissions by candidates was the use of diagrams, description of normal 
variation and only a superficial knowledge of compensatory mechanisms.
Syllabus: G1, 2d,g
References: Textbook of Medical Physiology, Guyton, Chp 61