Head Injury

Question 1

What does TBI stand for?

Why is it important? (3)

Answer 1

Traumatic brain injury

It is common, it significantly affects young adults, and prevention and treatment can make a difference.

Question 2

What is the UK incidence of TBI?

Answer 2

0.4 – 1% per year

Question 3

What % of A&E attendance was for TBI?

Answer 3

6% (700,000)

Question 4

Trauma is the leading cause of death for what age group?

Answer 4

Under 45s

Question 5

What is the principle determinant of long term outcome from poly-trauma?

Answer 5

TBI

Question 6

Head injury accounts for how many % of traumatic mortality?

Answer 6

50%

Question 7

What is the mortality (%) for severe head injury?

Answer 7

25%

Question 8

How many % of inpatients with head injury have long term disability?

Answer 8

50%

Question 9

What is the socio-economic burden of RTAs to Europe?

Answer 9

180 billion euros

Question 10

By how many % do seat belts reduce RTA mortality?

Answer 10

40-60%

Question 11

Has the mortality of severe head injury risen or fallen over the last 30 years? By how much?

Answer 11

Fallen from 50 to 25%

Question 12

What is the Munro-Kelly doctrine?

Answer 12

It explains the relationship between intracranial content (brain, CSF, venous and arterial blood) and intracranial pressure (ICP). The intracranial volume is fixed.
If there is a mass in the cranial cavity, this may be compensated for by displacement of CSF into the spine and of venous blood into the circulation.
If the mass gets large enough, there can no longer be compensation - it is now DECOMPENSATION. The ICP then starts to rise rapidly.

Question 13

Most organs are perfused with blood at mean arterial pressure (MAP). How is this different with the brain?

Answer 13

The brain is perfused at mean arterial pressure MINUS the intracranial pressure. This is the cerebral perfusion pressure.

CPP = MAP - ICP

Question 14

What happens to the perfusion to the brain when ICP increases?

Answer 14

As CPP = MAP - ICP, as ICP increases, CPP decreases. This means the brain becomes less perfused (cerebral blood flow falls).

Question 15

What is special about the neurons in the penumbra?

Answer 15

Contains more metabolically sensitive neurons

Question 16

Where are the three places herniation occurs?

Answer 16

Subfalcine
Tentorial (lateral or central)
Tonsillar

Question 17

What happens when the brain herniates and compresses CN III?

Answer 17

Dilated and fixed pupil

Question 18

What are Duret haemorrhages?

Answer 18

When the brain herniates, it can damage the brainstem and its vital centres (such as the respiratory centres in the pons and medulla). This is evidenced by Duret haemorrhages - haemorrhages in the pons.

Question 19

In terms of the meninges, where may haemorrhages occur? (3)

Answer 19

Extradural
Subdural
Subarachnoid

Question 20

How much does the head weigh?

Answer 20

7 kg

Question 21

Explain the molecular pathology of TBI.

Answer 21

1. Axons separate and retraction balls are seen
2. Neurons undergo apoptosis
3. Injured cells swell (as they have lost their energy and ion metabolism) = cytotoxic oedema

Question 22

Due to TBI and damage, what is happens (e.g. with amino acids, calcium and proteases) to cause neurogeneration?

Answer 22

Oxygen free radicals
Excitatory amino acids
Dynorphin
Calcium influx
Activation of proteases (causes neurodegeneration)

Question 23

What is ‘neuroprotection’ therapy?

Answer 23

Therapy aimed at preventing neuronal cell death after injury with the effect of improving outcome. Clinical trails have failed so far.

Question 24

Can the adult human brain repair itself?

Answer 24

Not really - it has negligible capacity for repair and no therapeutic intervention has been effective in changing this. There aren’t effective mechanisms for the generation of new neurons and growth of new axons.

Question 25

What changes are seen in a comatose patient in terms of circulation, respiration, ventilation etc? (5)

Answer 25

Inability to open the eyes, vocalise words and obey simple commands
Affects respiration and circulation
Depresses cough, gag and swallow
Slows ventilation (CO2 rises)
Decreases BP

Question 26

How can secondary brain injury be prevented?

Answer 26

By excellent resuscitation, restoring the airway, and immbolisation of cervical spine. This is to preserve brain perfusion.

Question 27

Why is it important to do an early CT scan?

Answer 27

To identify haematoma quickly so rapid referral to neurosurgery can be made

Question 28

In summary, what are the core principles management centres around? (4)

Answer 28

prevention
resuscitation
rapid neurosurgical intervention (if appropriate)
rehabilitation

Question 29

How does ICP predict outcome?

Answer 29

High ICP predicts poor outcome

Question 30

Patients in neurointensive care are hyperventilated. Why are these patients also sometimes sedated?

Answer 30

To reduce their oxygen requirements