Head Injury Flashcards
What does TBI stand for?
Why is it important? (3)
Traumatic brain injury
It is common, it significantly affects young adults, and prevention and treatment can make a difference.
What is the UK incidence of TBI?
0.4 – 1% per year
What % of A&E attendance was for TBI?
6% (700,000)
Trauma is the leading cause of death for what age group?
Under 45s
What is the principle determinant of long term outcome from poly-trauma?
TBI
Head injury accounts for how many % of traumatic mortality?
50%
What is the mortality (%) for severe head injury?
25%
How many % of inpatients with head injury have long term disability?
50%
What is the socio-economic burden of RTAs to Europe?
180 billion euros
By how many % do seat belts reduce RTA mortality?
40-60%
Has the mortality of severe head injury risen or fallen over the last 30 years? By how much?
Fallen from 50 to 25%
What is the Munro-Kelly doctrine?
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.
Most organs are perfused with blood at mean arterial pressure (MAP). How is this different with the brain?
The brain is perfused at mean arterial pressure MINUS the intracranial pressure. This is the cerebral perfusion pressure.
CPP = MAP - ICP
What happens to the perfusion to the brain when ICP increases?
As CPP = MAP - ICP, as ICP increases, CPP decreases. This means the brain becomes less perfused (cerebral blood flow falls).
What is special about the neurons in the penumbra?
Contains more metabolically sensitive neurons
Where are the three places herniation occurs?
Subfalcine
Tentorial (lateral or central)
Tonsillar
What happens when the brain herniates and compresses CN III?
Dilated and fixed pupil
What are Duret haemorrhages?
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.
In terms of the meninges, where may haemorrhages occur? (3)
Extradural
Subdural
Subarachnoid
How much does the head weigh?
7 kg
Explain the molecular pathology of TBI.
- Axons separate and retraction balls are seen
- Neurons undergo apoptosis
- Injured cells swell (as they have lost their energy and ion metabolism) = cytotoxic oedema
Due to TBI and damage, what is happens (e.g. with amino acids, calcium and proteases) to cause neurogeneration?
Oxygen free radicals Excitatory amino acids Dynorphin Calcium influx Activation of proteases (causes neurodegeneration)
What is ‘neuroprotection’ therapy?
Therapy aimed at preventing neuronal cell death after injury with the effect of improving outcome. Clinical trails have failed so far.
Can the adult human brain repair itself?
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.
What changes are seen in a comatose patient in terms of circulation, respiration, ventilation etc? (5)
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
How can secondary brain injury be prevented?
By excellent resuscitation, restoring the airway, and immbolisation of cervical spine. This is to preserve brain perfusion.
Why is it important to do an early CT scan?
To identify haematoma quickly so rapid referral to neurosurgery can be made
In summary, what are the core principles management centres around? (4)
prevention
resuscitation
rapid neurosurgical intervention (if appropriate)
rehabilitation
How does ICP predict outcome?
High ICP predicts poor outcome
Patients in neurointensive care are hyperventilated. Why are these patients also sometimes sedated?
To reduce their oxygen requirements
