Head Injury Flashcards
Why is traumatic brain injury a problem
- it is common
- it significantly affects young adults
- prevention and treatment can make a difference
Describe the epidemiology of traumatic brain injury
• 6% of A&E attendance
• UK incidence 0.4 – 1%/year
• 700,000 A&E attendances
• 110,000 admissions
• 4,000 neurosurgical interventions
• falls, assaults and RTAs
- roughly 25% mortality for severe head injury
- half of adult inpatients with head injury have long term disability
- estimated that the socio-economic burden of RTAs to Europe is 180 billion euros
the principles determinate of long term outcome from…..
- principle determinate of long term outcome from polytrauma and head injury accounts for 50% of traumatic mortality
what has made a difference to reducing the death from traumatic brain injury in the last 30 years
- over the last 30 years the mortality of severe head injury has fallen from 50% to 25%
- seatbelts reduce road traffic accident mortality by 40-60%
- speed limits, airbags, driver education, licensing, old age fall prevention, playground safety
what is the good thing and bad thing about the skull
- the skull provides some protection to he brain from trauma
- but if the brain swells or a haematoma takes up extra space then the brain will become squashed and this can cause the brain to become damaged
who came up with the idea that the skull is fixed
Munro-kelly Doctrine
what does the munro-Kelly Doctrine explain
- It explains the relationship between the intracranial content and the intracranial pressure
describe the physiology behind the munro-telly doctrine
- this is the idea that the intracranial volume is fixed
- the brain, CSF and blood are the usual contents
- if something else is added to that space for example in the context of trauma that can be a swollen bruised part of the brain or haematoma
- these to start with are compensated for by displacement of the CSF into the spine through the foramen magnum or the venous blood back into the circulation therefore this is compoesnated
- once these compensated mechanisms are exhausted there is no where else for them to go
- therefore the pressure ICP has to rise
- this is uncompensated and can happen quickly
what are the compensation mechanisms for the brain swelling
by displacement of the CSF into the spine through the foramen magnum or the venous blood back into the circulation therefore this is compensated as it makes more space for the brain
when the ICP increases what happens
- as the ICP increases there is effective perfusion pressure of the brain (cerebral perfusion pressure CPP) decreases
- As the CPP falls the cerebral blood flow falls
- therefore there is less perfusion to the brain and it becomes hypoxic
write the equation to work out CPP
- CPP=MAP-ICP
what can happen when ICP raises
- ICP can squeeze the brain out of the skull and cause herniation
name 4 different types of herniation
- subfalcine
- uncal
- tonsillar herniation
- lateral tentorial and central tentorial herniation
describe what happens in a subfalcine herniation
- this is when the medial part of the hemisphere is squeezed under the fall
- this part fo the brain is damaged and bruised and start to swell
- usually parts of the cingulate gyrus
- can also result in damage of some key vessels such as the anterior cerebral arteries
describe what happens in an uncal herniation
- compression of cranial nerve III
describe what happens in tonsils herniation
this is when the ICP rises and the tonsils of the brain are pushed through the foramen magnum
- this can squeeze the medulla and upper spinal cord as well as the bottom of the cerebellum
- damages processes of breathing, control of blood pressure and pulse rate and this is often terminal
describe what happens in lateral tentorial and central tenurial herniation
this is herniation through the tentorium cerebellum and the medial aspect of the temporal lobe herniates through the tentorial notch,
- this also starts to squeeze the midbrain = pupil can start to dilate
where is the extradural space
this is between the periosteal layer and meningeal layer of the dura mater
describe what shape an epidural haemotoma is
biconvex
- can be due to damage to a middle meningeal artery
where is the subdural space
between the dura mater and subarachnoid
where is the subarachnoid space
between the subarachnoid and Pia mater
what shape is a subdural haemoatoma
sickled shaped
what do sinuses do to the skull
- these are associated with the nose and ears
- make skull lighter
- allows the skull to have responses
- filter the air as it comes in to remove the microbes
describe how the brain can become infection
- sinuses are closed to the Brain
- head injury can damage these spaces and cause them to fill up with blood, this happens when there is fracture to the base of the skull
- this is important as the sinuses are usually filled with mucous and bacteria therefore if these enter the brain this can lead to assess formation and meningitis
