Raised intracranial pressure

Question 1

If the brain enlarges, what physiological adaptations are in place to avoid a rise in pressure?

Answer 1

Blood escapes from the cranial vault to avoid the rise in pressure
Venous sinuses are flattened and there is little or no CSF

Question 2

If there is an increase in brain volume beyond the physical adaptations, what does this result in?

Answer 2

Rapid increase in ICP

Question 3

Causes of raised ICP

Answer 3

Increased CSF (hydrocephalus)
Focal lesion in the brain (space occupying lesion)
Diffuse lesion in the brain (oedema)

Question 4

Effects of raised ICP

Answer 4

Intracranial shifts and herniation

This results in asymmetric expansion of the cerebral hemisphere

Question 5

Subfalcine herniation

Answer 5

Unilateral or asymmetrical expansion of the cerebral hemisphere displaces the cingulate gyrus under the falx cerebri

Question 6

Subfalcine herniation - which artery can get compressed

Answer 6

Anterior cerebral artery
- weakness and/or sensory loss in the leg, because of ischaemia to the primary motor and/or sensory cortex in these midline areas

Question 7

Tentorial (uncal) herniation

Answer 7

Medial aspect of the temporal lobe (hippocampal uncus and parahippocampal gyrus) herniates down through to the tentorium cerebelli

Question 8

Tentorial (uncal) herniation - which structure can get compressed

Answer 8

Ipsilateral CN III and its parasympathetic fibres

- leads to pupillary dilation and impairment of ocular movements on the side of the lesion

Question 9

Tonsillar (cerebellar) herniation “coning”

Answer 9

Displacement of the cerebellar tonsils through the foramen magnum (cerebellum sucked through the foramen magnum)

Question 10

Tonsillar (cerebellar) herniation “coning” - why is this life threatening

Answer 10

Causes brainstem compression and compromises vital respiratory centres in the medulla oblongata

Question 11

Transcalvarial herniation

Answer 11

A swollen brain will herniate through any defect in the dura and skull

Question 12

Transcalvarial herniation - clinical features

Answer 12

Reduced consciousness
Dilation of pupil on same side as mass lesion
Bradycardia

Question 13

Clinical signs

Answer 13

Papilloedema
Headache
N+V
Neck stiffness

Question 14

Why do you get papilloedema

Answer 14

Occurs due to pressure on the optic nerve

Question 15

Headache

Answer 15

Worse on lying down, coughing, sneezing, straining

Question 16

Neck stiffness

Answer 16

Due to pressure on dura around cerebellum and brainstem

Question 17

Nausea and vomiting

Answer 17

Due to pressure on vomiting centres in pons and medulla