1.11 Acute Insults to the CNS: Traumatic Brain Injury Flashcards
What is the biggest cause of death and disability (combined) in adults under 45?
Traumatic brain injury
What GCS corresponds to mild, moderate, and severe brain injury?
13-15: Mild
9-12: Moderate
3-8: Severe
What periods of unconsciousness correspond to what severity of TBI?
Mild: <30mins
Moderate: 30mins-24hrs
Severe: Over 24hrs
What periods of post-traumatic amnesia correspond to what severity of TBI?
Mild: Less than a day
Moderate: Days to a week
Severe: More than a week
Chronically, what pathologies is TBI associated with?
- Seizures
- Sleep disorders
- Neurodegenerative diseases
- Psychiatric disorders
Differentiate between focal vs diffuse TBI
Focal: one area of the brain
Diffuse: more than one area of the brain
Are primary/secondary TBI pathologies treatable?
- Primary can only be prevented by preventing the trauma in the first place
- Secondary can be treated, since it is occurring after the initial insult itself
What are some potential secondary consequences of traumatic brain injury?
- Neuroinflammation
- Cerebral oedema
- Oxidative stress
Summarise the pathology of penetrating TBIs
Laceration of brain tissue, crushing of brain tissue, intracerebral haematoma and ischaemia secondary to clotting.
Summarise the pathology of blast TBIs
Blast wave induces sudden increase in intracranial pressure, particularly at interfaces between CSF and brain. Results in penetration/cavitation of brain tissue, damage to blood vessels, and disruption of axonal pathways.
What causes focal brain injuries?
Object striking the head, or brain coming into contact with skull
Coup vs contrecoup injuries
Coup: At site of impact
Contrecopu: directly opposite
What are some downstream pathologies of focal TBI?
- Cranial fracture
- Intracranial haemorrhage
- Bruising
What is unique about TBIs at the base of the skull?
- Can cause tearing of meninges and leaking of CSF
- Can damage foramen of blood vessels/nerves
Describe the appearance of extradural haemorrhage on CT imaging
- Biconvex in shape (curve away from the skull)
- Limited by cranial sutures
Where is the most common site of an extradural haemorrhage?
- Pterion (pteron; Hermes)
- Point at which temporal, parietal, frontal, and sphenoid bones meet
Which of a subdural vs extradural haemorrhage worsens faster? Why?
- Extradural worsens faster
- Subdural is usually venous, so progresses slower than extradural, which is usually arterial
Which veins are commonly torn in subdural haemorrhage?
Bridging veins
Describe the imaging presentation of a subdural haemorrhage
Run with curvature of the brain.
Which has worse prognosis: subdural haemorrhage or extradural haemorrhage?
Subdural; associated with more brain injury
Cerebral contusions mech
- Brain comes into contact with irregular bony protuberances of skull
- Damages small blood vessels and other components of brain parenchyma
- Causes bruising (“contusions”); creating toxic environment that damages surrounding tissue
True or false: diffuse brain injury requires the brain to come into contact with the skull
False. It’s more likely to be axonal/vascular damage in response to acceleration/deceleration
Why is the brain particularly vulnerable to traumatic injury?
- Large weight relative to body
-High white:grey ratio (white is more vulnerable to damage) - Large size
What is the biggest cause of widespread axonal damage?
Secondary injury processes. Axotomy is actually quite rare.
What are the two main component proteins of the axonal structure (and their functions)?
- Neurofilaments: main structural protein
- Microtubules: highways for transport to and from soma
Describe secondary axonal injury (specific mechanism)
- Microtubules tear apart in response to inflammation
- Calcium leaks into axons, triggering enzymatic cascade that worsens damage to cytoskeleton and microtubules
- Triggers apoptosis
Describe the pathology of hypoxia/ischaemia secondary to TBI
- Damage to blood vessels leads to hypoperfusion, hypoxia, and ischaemia
- Can contribute to oedema, and occurs alongside increased glucose demand (extra harmful)
Physical symptoms of concussion
- Headaches
- Nausea
- Dizziness
- Sensitive to light and noise
Mental symptoms of concussion
- Fogginess
- Difficulty concentrating and remembering
Sleep-based concussion symptoms
- Sleeping more/less
- Difficulty falling/staying asleep
Emotional and behavioural concussion symptoms
- Sadness
- Anger
- Frustration
- Irritable
True or false: concussion, particularly repeated concussion, may be linked to later development of neurodegenerative disease
True
Why is concussion difficult to diagnose?
- No imaging abnormalities
- No biomarkers/routine tests
- Other things (e.g. hangover) show up as false positives
- Subjectivity of symptoms
List important history points in a suspected concussion
- Details of event (eye witnesses?)
- Loss of consciousness, amnesia, seizures?
- Previous concussions? Psychiatric illnesses? Migraines? Seizures?
- Improvement/deterioration (bleeds)?
Describe how a person should re-enter life post-concussion
- Wait 1-2 days
- Do something (not sport etc.), and see if it causes symptoms. If so, rest for longer.
- When re-entering sport, start with lowest risk activity, and move from there
Describe the pathophys of chronic traumatic encephalopathy
- Tau protein leaves microtubules, destabilising axons and leading to axonal damage
Describe the pathophys of concussion
- Initial trauma sets of secondary injurious processes, leading to axonal death
- Indiscriminate neurotransmitter release causes increase in ion pump activity
- Increased glucose demand, yet decreased blood supply
Describe the shape of the increase in ICP. Why does this happen?
- As the pressure rises, autoregulatory mechanisms fail.
- This leads to decompensation, causing a sharp upward increase in ICP.
Describe the acute management of traumatic brain injury
- DR ABCDE
- Protect airway, ventilate, administer oxygen
- Maintain systolic >90
- Record GCS
- Check pupil size
- Be careful of cervical spine
This is all with the idea of preventing 2° injury
