9.3: Raised Intracranial Pressure

Question 1

What is normal intracranial pressure?

Answer 1

5 to 15 mmHg

Question 2

What is the pathophysiology behind why a brain injury leads to raised intracranial pressure?

Answer 2

Reduced blood supply to brain (eg if tumour)
Reduced ATP supply
NA/K-ATPase function is impaired
Na accumulates inside the cell
Water follows Na
Cerebral oedema
Further swelling

Question 3

What are some signs and symptoms of RICP?

Answer 3

Generalised headache (worse in morning, when coughing or bending)
Nausea and vomiting
Visual disturbances (compression of optic nerve)
CN6 nerve palsy (lateral rectus)
Loss of consciousness
Cushing’s reflex (triad = bradycardia, High BP, raised RR)

Question 4

Where is CSF stored in the brain?

Answer 4

Subarachnoid space

Question 5

What is hydrocephalus?

Answer 5

Accumulation of CSF due to imbalance between production and absorption, with subsequent enlargement of the ventricles.

Question 6

What is non communicating hydrocephalus?

Answer 6

Due to blockage within the ventricles, commonly in cerebral aqueduct (eg due to tumour)
Can also be congenital
Or due to tumours eg menigioma

Question 7

What is communicating hydrocephalus?

Answer 7

When there is communication between the ventricles and the subarachnoid space, so the problem is outside the ventricular system
E.g. most meningitis infection, due to reduced absorption (blockage of venous system), increased production (choroid plexus papilloma),

Question 8

What is idiopathic intracranial hypertension?

Answer 8

Usually in obese young women after weight gain
Signs of RICP but investigations normal

Tx: weight loss, mannitol, CSF shunts

Question 9

What is the Cushings reflex in response to RICP?

Answer 9

Cushing’s triad: bradycardia, High BP, High RR

(Raised pressure causes arteriolar compression which activates the sympathetics which causes HTN and tachycardia to try to restore blood flow to the ischaemic brain. Baroreceptors in the aortic arch detect this increased BP and trigger parasympathetics via the vagus nerve. This induces bradycardia. Compression of the brainstem results in irregular breathing hence raised RR)