Raised Intracranial Pressure

Question 1

What is it?

Answer 1

As the brain and ventricles are enclosed by a rigid skull, they have a limited ability to accommodate additional volume. Additional volume (e.g. haematoma, tumour, excessive CSF) will therefore lead to a rise in intracranial pressure (ICP).

Question 2

Pathophysiology?

Answer 2

the normal ICP is 7-15 mmHg in adults in the supine position
cerebral perfusion pressure (CPP) is the net pressure gradient causing cerebral blood flow to the brain
CPP = mean arterial pressure - ICP

Question 3

Causes

Answer 3

idiopathic intracranial hypertension
traumatic head injuries
infection
meningitis
tumours
hydrocephalus

Question 4

Features

Answer 4

headache
vomiting
reduced levels of consciousness
papilloedema
Cushing’s triad
widening pulse pressure
bradycardia
irregular breathing

Question 5

Investigations and monitoring

Answer 5

neuroimaging (CT/MRI) is key to investigate the underlying cause
invasive ICP monitoring
catheter placed into the lateral ventricles of the brain to monitor the pressure
may also be used to take collect CSF samples and also to drain small amounts of CSF to reduce the pressure
a cut-off of > 20 mmHg is often used to determine if further treatment is needed to reduce the ICP

Question 6

Management

Answer 6

investigate and treat the underlying cause
head elevation to 30º
IV mannitol may be used as an osmotic diuretic
controlled hyperventilation
aim is to reduce pCO2 → vasoconstriction of the cerebral arteries → reduced ICP
leads to rapid, temporary lowering of ICP. However, caution needed as may reduce blood flow to already ischaemic parts of the brain
removal of CSF, different techniques include:
drain from intraventricular monitor (see above)
repeated lumbar puncture (e.g. idiopathic intracranial hypertension)
ventriculoperitoneal shunt (for hydrocephalus)