Raised ICP & hydrocephalus

Question 1

What are the causes of a raised ICP?

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

What is the normal ICP in adults

Answer 2

7-15 mmHg

Question 3

What is the cerebral perfusion pressure?

Answer 3

The net pressure gradient causing cerebral blood flow to the brain

Question 4

What is the equation for cerebral perfusion pressure?

Answer 4

CPP = mean arterial pressure – ICP

Question 5

What are the signs of hydrocephalus?

Answer 5

Headaches, vomiting, reduced levels of consciousness, Papilledema,

Question 6

What is the Cushing’s triad present in hydrocephalus?

Answer 6

Widening pulse pressure, Bradycardia, irregular breathing

Question 7

What investigations are done for hydrocephalus?

Answer 7

CT/MRI

Invasive ICP monitoring

Question 8

What are the management plans for hydrocephalus?

Answer 8

investigate and treat the underlying cause
head elevation to 30º
IV mannitol may be used as an osmotic diuretic

Question 9

What are some of the ways to remove excess CSF in hydrocephalus?

Answer 9

Drain from intraventricular monitor (see above)

Repeated lumbar puncture (e.g. idiopathic intracranial hypertension)

Ventriculoperitoneal shunt (for hydrocephalus)

Question 10

What is the pathway of CSF production?

Answer 10

Choroid plexus (lateral ventricles) → ventricular system → subarachnoid space (Magendie and Luschka) → venous system (arachnoid granulations)

Question 11

Hydrocephalus can be broadly divided into two categories; what are they?

Answer 11

Obstructive (‘non-communicating’) hydrocephalus

Non-obstructive (‘communicating’) hydrocephalus

Question 12

What is an Obstructive (‘non-communicating’) hydrocephalus?

Answer 12

Due to a structural pathology blocking the flow of CSF.

Dilatation of the ventricular system is seen superior to site of obstruction

Question 13

What is an Non-obstructive (‘communicating’) hydrocephalus?

Answer 13

Non-obstructive hydrocephalus is due to an imbalance of CSF production and absorption.

Question 14

What are the causes of Obstructive (‘non-communicating’) hydrocephalus?

Answer 14

Tumours, acute haemorrhage (e.g. subarachnoid haemorrhage or intraventricular haemorrhage) and developmental abnormalities (e.g. aqueduct stenosis).

Question 15

What are the causes of Non-obstructive (‘communicating’) hydrocephalus?

Answer 15

Caused by an increased production of CSF (e.g. choroid plexus tumour (very rare)) or more commonly a failure of reabsorption at the arachnoid granulations (e.g. meningitis or post-haemorrhagic).

Question 16

What is a Normal pressure hydrocephalus?

Answer 16

A unique form of non-obstructive hydrocephalus characterized by large ventricles but normal intracranial pressure.

Question 17

What are the features of Normal pressure hydrocephalus?

Answer 17

Dementia, incontinence, and disturbed gait

Question 18

What investigations are dine for hydrocephalus?

Answer 18

CT and MRI (Better detail)

Question 19

Why should a lumbar puncture not be done in obstructive hydrocephalus?

Answer 19

The difference of cranial and spinal pressures induced by the drainage of CSF will cause brain herniation

Question 20

When is a external ventricular drain (EVD) used in hydrocephalus?

Answer 20

Used in acute, severe hydrocephalus and is typically inserted into the right lateral ventricle and drains into a bag at the bedside

Question 21

What are other treatments for hydrocephalus?

Answer 21

Surgery for obstructive
Carbon anhydrase inhibitors (Acetazolamide, Topiramate)
Diuretics to reduce BP
CSF diversion
LP- or VP-shunt