Pathology of Head Injury Flashcards
What is primary insult in head injury?
Focal and/or diffuse brain trauma
What are secondary insults (can result from primary insult) in head injury?
Hypotension
Hypoxia
Infection
Haematoma
How is conscious level assessed?
Glasgow Coma Scale (scored out of 15)
How does the GCS correlate with severity of head injury?
13-15 = mild injury 9-12 = moderate injury 3-8 = severe injury
Give 7 significant complications of head injury?
- Permanent physical disability
- Post traumatic epilepsy
- Intracranial infection
- Psychiatric illness
- Chronic subdural haemhorrage
- ‘Punch-drunk’ dementia
- Fatal outcome (uncommon)
What is a common site for laceration?
The scalp (because it is closely applied to the skull and tearing associated with application of force more likely to occur - anvil effect)
What do scalp lacerations commonly mimic?
An incised wound (important to differentiate as different mechanism of injury - knife)
Where may bruising/bleeding occur when not on outer surface of scalp?
May occur in the deeper layers of the scalp or between scalp and skull (particular note in infant head injury)
What are the 2 elements to the skull?
- Skull vault - frontal, temportal, occipital bone + sutures
- Skull base - anterior, middle, posterior cranial fossae
What are the 5 types of skull fracture?
Linear Depressed Comminuted (mosaic) Ring Contre-coup
Which is the simplest skull fracture?
Linear - ‘hinge’ fracture, fractures can spread along and reach suture and split suture (‘sprung’)
What does a depressed fracture commonly arise from?
Impact on protruding object or blunt force e.g. fro hammer
What are the risks from a depressed fracture?
Meningitis and post-traumatic epilepsy (fragments pushed inwards to damage meninges, blood vessels + brain)
What is a comminuted fracture?
Fragmented skull
What is a ring fracture?
Fracture line encircling foramen magnum caused by fall from height (usually land on feet but can be head)
What does a contre-coup fracture result from?
A fall onto back of head
What does a contre-coup fracture present as?
Fracturing of orbital plates; black ‘panda eyes’ classic of basal skull fractures
How are intracranial hamehorrhages named?
By their position within the skull in relation to the meninges i.e. extradural, subdural, subarachnoid
What does the accumulation of blood within the rigid skull in haemhorrage cause?
Raised ICP - results in brain compression causing symptoms like reduction in conscious level
What will ultimately occur as ICP increases without intervention (e.g. drill holes in skull)?
Death by compression of brainstem due to herniation of cerebellar tonsils into the foramen magnum
What is an extradural haemhorrage?
Bleeding occuring between the dura and skull
What do vast majority EDH arise from?
Damage to artery in association with skull fracture (80-90%); sometimes large venous channels can cause
Which artery is classically responsible for EDH?
Middle meningeal artery
Again, what does the accumulation of blood in EDH cause?
Raised ICP and associated symptoms
What type of interval can occur during an EDH?
Lucid interval - victim can then deteriorate catastrophically later
What is a subdural haemhorrage?
Bleeding occuring beneath the dura and above the arachnoid
What is SDH usually caused by?
Bleeding from bridging veins which pass from the surface of the brain to drain into large venous channels within the dura
Which type of motion can cause veins to stretch and be torn due to relative movement between brain and dura?
Any motion which causes rotational or ‘shearing’ forces; associated with trauma like an accelerated fall; frequently occurs without skull fracture
Which individuals are at increased risk of SDH?
Individuals with atrophic (small) brains because smaller brain has greater capacity for movement and veins may already be stretched
What type of intervals can occur in SDH?
Lucid interval (classically long - GCS 14/15 then gradually become comatose)
Can you get chronic SDH?
Yes, particularly in elderly (may cause chronic confusion - mistaken for dementia)
What is a subarachnoid haemhorrage?
Bleeding beneath arachnoid membrane (and above brain); most common haemhorrage
What is the most common cause of SAH?
Rupture of cerebral artery ‘berry’ aneurysm (within circle of willis); blood can track very far because tissue is looser
What does SAH present as?
Thunderclap headache (sudden onset)
What is SAH frequently seen in association with?
Cerebral contusions (bruising to brain)
What is traumatic brasal SAH?
A specific entity in forensic medicine - person falls down dead in immediate cardiac arrest - very sudden blow to neck or side of head (damage to brainstem); thought to be due to rapid movement causing immediate rupture of vertebral arteries
What is cerebral oedema?
Generalised brain swelling in response to focal/diffuse injury; can develop in minutes
What can cerebral oedema cause?
Secondary brain ischaemia - further swelling; often THE cause of death in head injury due to raised ICP
What is cerebral contusion/laceration?
Direct mechanical damage to brain surface
What can cause laceration to the brain?
Very high forces are required e.g. RTA or fall from height
What are contusions?
Patchy areas of haemhorrage within grey matter (cortical layer) - if extensive enough will go to white
What are 2 types of contusion?
Coup (contusion directly under site of impact) + contre-coup (other side of head)
What can happen with contusion injuries over a few days?
Patient is fine initially, then suddenly become comatose a few days later prob due to extension of contusional injuries
What is diffuse axonal injury?
Tearing of nerve fibres in white matter of brain
What is diffuse axonal injury called in terms of trauma?
tDAI
How is tDAI diagnosed?
Microscopy of brain tissue - swelling of axons (can try and date survival times etc) (but may get concomitant damage to small blood vessels within brain which raise suspicions of tDAI)
What are tDAI usually caused by?
Scenarios associated with tDAI - vehicular collisions and falls from height - serious rotational forces
What parts of the brain are particularly susceptible to tDAI?
Corpus callosum, para-sagittal white matter, posterior internal capsule, dorsolateral aspects of rostral brainstem, cerebellar peduncles
What state are patients usually in when tDAI is fully developed?
Coma
How is tDAI graded?
1 to 3; grade 2/3 would expect patient to be unconscious immediately
