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