Intracranial Pressure and Cerebral Blood Flow

Question 1

What is normal ICP?

Answer 1

5-15cm of water

Question 2

Where is CSF produced?

Answer 2

Choroid plexus

Question 3

There are transient increases and decreases in ICP during which common activitie?

Answer 3

Straining
Sneezing
Standing up from sitting

Question 4

An ICP above what level is considered pathological?

Answer 4

Beyond 20cm of water

Question 5

If there are any space occupying lesions, what happens to ICP?

Answer 5

It increases

Question 6

If there was a space occupying legion in the brain, what would happen to compensate for this change?

Answer 6

Compensation would occur by reduction of venous blood.
There would be displacement for CSF towards the spinal column.
Reduction of CSF.

Question 7

If there is not any compensation for a space occupying lesion by the venous blood and CSF, what happens?

Answer 7

ICP rises

Question 8

Briefly describe the pathology of raised ICP.

Answer 8

Raised ICP causes shifts in different parts of the brain.
There can be reduction of blood flow leading to ischaemia.
There is reduced energy production and pump failure leading to cellular dysfunction.
Therefore, toxic metabolites build up leading to cell death.

Question 9

ICP can be measured and seen in waves. There are three components to the waves- P1,2,3.
What do these notches correspond to?

Answer 9

Arterial wave of pulse

Question 10

Which two components are responsible for the variation of ICP?

Answer 10

Arterial pulse
Respiration

Question 11

What value is normal cerebral blood flow?

Answer 11

700ml/min
50ml/100g/min

Question 12

How much for the cardiac output does cerebral blood flow account for?

Answer 12

Roughly 14%

Question 13

Which area of the brain receives more blood per minute, the white or grey matter?

Answer 13

Grey matter

(70ml/100g / min compared to 20ml/100g/min in white)

Question 14

Cerebral perfusion pressure?

Answer 14

Difference between MAP and ICP

Question 15

Cerebro-vascular resistance?

Answer 15

Resistances offered by cerebral vasculature to flowing blood

Question 16

Autoregulation?

Answer 16

Ability of brain to maintain constant blood flow over wide range of pressures

Question 17

What does cerebral blood flow ultimately depend on?

Answer 17

MAP
ICP
Vascular resistance
Autoregulatory mechanisms of brain

Question 18

If there is low vascular resistance, what will the flow be like?

Answer 18

High flow

->and if high resistance, low flow

Question 19

The brain has the ability to increase blood flow to specific regions in the brain when they are active. Give an example of this.

Answer 19

Increasing blood flow to temporal lobe during speech

Question 20

Presence of metabolites in the blood can have a significant influence of cerebral blood flow.
Give an example of a metabolite which influences this blood flow.

Answer 20

Carbon dioxide

Question 21

If carbon dioxide is low in the blood, what happens?

Answer 21

Vasoconstriction

->vasodilation if the carbon dioxide levels are high

Question 22

What does brain tissue use for metabolism?

Answer 22

Glucose and ketones

->brain tissues have no stored energy source

Question 23

What effect will impaired blood flow have on energy production?

Answer 23

Lead to mitochondrial energy production failure within seconds and cell death within minutes

Question 24

Which abilities does the brain lose when it’s injured?

Answer 24

Ability to autoregulate leading to hypotension/hypertension, hypoxia and raised ICP

Question 25

Which type of injuries can caused raised ICP?

Answer 25

Severe traumatic

Question 26

If someone has raised ICP, what gets continuously monitored?

Answer 26

ICP
Blood pressure

Question 27

List some clinical conditions in which ICP is measured.

Answer 27

Hydrocephalus
Stroke
Venous outflow obstruction
Tumours
Brain haemorrhage