10. CSF, BBB, ICP

Question 1

How much CSF is found in the sub-arachnoid space?

Answer 1

117ml

Question 2

How much CSF is found in the ventricles?

Answer 2

23 ml

Question 3

What are the functions of CSF?

Answer 3

Cushioning
Chemical stability
Allows brain to exist in neutral buoyancy

Question 4

Where is CSF produced?

Answer 4

Choroid plexus

Around blood vessels and along ventricular walls

Question 5

What is the structure of the choroid plexus?

Answer 5

2 cells thick: endothelial cells of capillary wall and ependema
Tight junctions in ependyma

Question 6

What are the functions of the tight junctions in the ependyma?

Answer 6

Seals capillary walls to prevent unwanted substances entering CSF
Impermeable to water-soluble solutes, permeable to lipid soluble (these can dissolve in the cell membranes)
Dependable on transporters for water soluble

Question 7

What is the difference in composition between the CSF and plasma?

Answer 7

In CSF:
more Na+ and Cl-
Less K+ and glucose
no protein

Question 8

What forms the blood-CSF barrier?

Answer 8

Choroid plexus
Other brain capillaries
Transporters

Question 9

What vertebral level is a lumbar puncture needle inserted into?

Answer 9

L3/4 or L4/5

Question 10

What colour is CSF normally?

Answer 10

Colourless

Question 11

What colour is CSF in a sub-arachnoid haemorrhage?

Answer 11

Yellow

Question 12

What is the difference in a CSF sample from a patient with meningitis?

Answer 12

Increased WBCs

Question 13

What is the difference in a CSF sample from a patient with multiple sclerosis?

Answer 13

Associated antibodies present

Question 14

What is normal CSF/intercranial pressure?

Answer 14

10 mmHg

Question 15

What is hydrocephalus?

Answer 15

Abnormal accumulation of CSF due to excessive production, obstruction in circulation or faulty reabsorption
Ventricles enlarge and brain is flattened against the skull

Question 16

What conditions are associated with hydrocephalus?

Answer 16

Mental disability
Tunnel vision
Convulsive episodes

Question 17

What are common causes of infantile hydrocephalus?

Answer 17

Stenosis or inflammation of aqueduct of sylvius

Spina bifida

Question 18

What are common causes of adult hydrocephalus?

Answer 18

Obstruction of aqueduct

Obstruction of outflow from 4th ventricle

Question 19

What is a contracoup injury?

Answer 19

Brain is driven against the opposite side of the skull to where a blow hits

Question 20

What is a depressed skull fracture?

Answer 20

Bone is driven into brain tissue

Question 21

What is the blood brain barrier made up of?

Answer 21

Walls of cerebral capillaries
Transporters
Astrocytes

Question 22

How do brain capillaries differ to peripheral capillaries?

Answer 22

Lower permeability to water and impermeable to solutes due to BBB

Question 23

In what case is the BBB often absent?

Answer 23

In blood vessels associated with tumours

Plasma proteins will enter ICF of brain tumours

Question 24

What is the Monroe-Kellie doctrine?

Answer 24

Brain, brain fluid, blood and CSF are all incompressible

ICP is directly related to the volume of these contents

Question 25

What are the symptoms of increased intercranial pressure?

Answer 25

Headache, nausea, restlessness Neural dysfunction Papilloedema Cushing's reflex

Question 26

What is papilloedema?

Answer 26

Swelling of the optic disc

Question 27

What triggers Cushing's reflex?

Answer 27

Brain is severely hypercapnic and hypoxic | Triggers vasomotor centre in medulla

Question 28

Give the steps of Cushing's reflex?

Answer 28

1. Peripheral vasoconstriction (reroute blood to brain) 2. Results in increased BP (increase cerebral perfusion) 3. Increased firing of baroreceptors 4. Increased activity of cardio-inhibitory centre Reflex bradycardia