CSF and ICP

Question 1

What pathologies can cause raised ICP?

Answer 1

Haemorrhage e.g. due to trauma
Vasogenic oedema
Cytotoxic oedema
Influx of inflammatory mediators
Space occupying lesion

Question 2

What is the cellular effect of raised ICP?

Answer 2

Decreased cerebral perfusion: ischaemia, leading to infarction

Question 3

What is the anatomical effect of raised ICP?

Answer 3

Herniation syndromes

• subfalcine herniation (affects medial motor cortex)
• uncal herniation (affects CrN III)
• foramen magnum herniation (affects brain stem)

Question 4

What is the total volume of CSF in the body?

Answer 4

150ml (half intracranial, half in spinal cord)

Question 5

Describe the functions of CSF

Answer 5

Buoyancy; reduced the net weight of the brain
Protection from trauma; shock absorption
Regulation of ICP
Homeostasis e.g. pH
Waste removal

Question 6

Describe the normal composition of CSF

Answer 6

No RBCs
A few WBCs
Glucose (40-80mg/100ml)
Protein (15-45mg/100ml)
Chloride
Sodium

Question 7

Where does CSF drain back into the venous circulation?

Answer 7

Arachnoid granulations

Question 8

Where is the choroid plexus located and what is its function?

Answer 8

Floor of the lateral ventricles and the roofs of the third and fourth ventricles
Produces CSF

Question 9

Define the two types of hydrocephalus

Answer 9

Obstructive: blockage of outflow from ventricles
Communicating: blockage at the level of the arachnoid granules, causing a mismatch between production and absorption of CSF

Question 10

What investigations should be carried out when hydrocephalus is suspected?

Answer 10

Fundoscopy (look for papilloedema secondary to
  raised ICP)
Head CT (look for reduced clarity of ulci and gyri, and
  dilated ventricles)

Question 11

What is the significance of normal pressure hydrocephalus?

Answer 11

It is a potentially reversible dementia

Question 12

Describe the classical triad of symptoms of normal pressure hydrocephalus

Answer 12

Dementia (confusion)
Gait disturbance (magnetic gait)
Urinary incontinence

Question 13

How is hydrocephalus treated?

Answer 13

Surgical insertion of a CSF shunt to create a drainage route for CSF that is alternative to the arachnoid granules
- works because NPH is a communicating hydrocephalus

Question 14

What is normal pressure hydrocephalus?

Answer 14

The condition of ventricular dilatation in the absence of raised CSF pressure on lumbar puncture

Question 15

How is hydrocephalus treated in emergency situations?

Answer 15

CSF drainage

Question 16

What is the medical treatment for hydrocephalus? Is this long term or short term?

Answer 16

Carbonic anhydrase inhibitor such as acetazolamide

• reduces CSF production from choroid plexus
• short term measure

Question 17

Describe the potential complications of shunts

Answer 17

Over-drainage; risk of low pressure headaches or
subdural haematoma
Under-drainage
Blockage
Infection; often caused by skin flora and hard to treat
Disconnection
Seizures
Distal end problems; abdominal hernias, cardiac
arrhythmias

Question 18

What is xanthochromic CSF?

Answer 18

CSF is yellow due to presence of blood breakdown products (bilirubin)
Most commonly seen in SAH (12 hours after onset)

Question 19

What checks should be carried out before performing a lumbar puncture?

Answer 19

Patient should be conscious
No focal neurological deficit (LP dangerous if patient has raised ICP)
CT/MRI to rule out intracranial mass lesion (again due to risks associated with raised ICP)
No infection at the site of needle insertion
Ensure that the patient is not on anticoagulants
Must get verbal consent from the patient