Raised intracranial pressure

Question 1

how does increased brain volume lead to raised intra cranial pressure?

Answer 1

Phase of compensation due to reduced csf

Increased volume leads to increased pressure exponentially

Question 2

what effect does high ICP have on a brain scan?

Answer 2

Press on adjacent structures - mass effect, midline shift

Question 3

how does a high ICP caused internal hydrocephalus?

Answer 3

Compresses outflow to ventricles

Question 4

how does a raised ICP cause herniation?

Answer 4

Pressure gradients develop across holes in skull - e.g. foramen magnum, tentorium cerebelli = forces brain tissue through the hole, herniation
CSF removal = exacerbation of pressure gradient = herniation (think about lumbar puncture)
Herniation = compression on structures

Question 5

what is lateral tentorial herniation?

Answer 5

compression of midbrain, oculomotor nerve compressed so down and out eye and pupil dilates and ptosis, compression of posterior cerebellar artery (occipital infarction) , compressed cerebral peduncle contralateral causes hemiparesis on same side of compression, brainstem compression = bleeding into medulla
can be fatal

Question 6

what is tonsillar herniation?

Answer 6

the movement of the cerebellar tonsils through the foramen magnum, compression of medulla and cardio respiratory centres = death