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Neurotrauma > Traumatic Brain Injury > Flashcards

Traumatic Brain Injury Flashcards

1
Q

What is TBI?

A

A non-degenerative, non-congenital insult to the brain from an external mechanical force to the head, face or spine possibly leading to permanent or temporary impairment of cognitive, physical and psychosocial functions with an associated diminished or altered state of consciousness

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2
Q

Whom does TBI primarily affect?

A

Males ~80%

Under age of 45

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3
Q

In what ways can TBI be classified?

A

Severity - GCS, duration of LOC, length of post traumatic amnesia
Location and appearance - focal injury or diffuse injury

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4
Q

What is the significance of post traumatic amnesia in TBI?

A

The longer you are aren’t able to form memories after TBI the more likely you are to have cognitive dysfunction

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5
Q

Focal injuries vs diffuse injuries

A

Focal injuries - contusions, intracranial haemorrhage

Diffuse injuries - most injuries, not visible on a CT scan

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6
Q

What proxy is used to define some neurological injuries?

A

Blood - often refer to where the haemorrhage is e.g. subdural

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7
Q

What is the primary injury in TBI?

A

A mechanical event and occurs at the time of injury. Considered to be irreversible i.e. straining/tearing of axons and tearing of vessels

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8
Q

What is the secondary injury in TBI?

A

Several delayed pathological process which occur as a result of the primary injury e.g. ICP, Ischaemia, Oxygen free radicals

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9
Q

How would a diffuse absurd injury appear on a CT scan?

A

Not many abnormalities, some small dots indicating small haemorrhages. The damage is at an axonal level and so not visible on scans.

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10
Q

What level of consciousness would a patient with a diffuse absurd injury have?

A

In coma, patients present with LOC from outset

May be in the coma for a long period of time and may never emerge from it

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11
Q

What is associated with diffuse absurd injuries?

A

Vegetative state, disability and poor outcomes

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12
Q

What causes diffuse absurd injuries and how does velocity affect the injury?

A

Caused by acceleration/deceleration and rotational forces (common in RTC).
The stronger the forces applied the deeper the impact of damage - high velocity injuries cause damage to the midbrain and thalamus

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13
Q

What is an extradural haemorrhage and what are its characteristics?

A

Blood accumulates between the skull and dura mater.
Lens like appearance of a scan
Patients often have a lucid interval

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14
Q

What is a lucid interval in terms of TBI?

A

Initial brief LOC which pt recovers from. Pt then develops a headache and eventually seizes

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15
Q

What is a subdural haemorrhage and what are its characteristics?

A

Bleeding between dura mater and arachnoid mater
Biconcave shape on scan
Associated with high velocity injuries
Signs: reduced GCS, drowsiness, headache, pupillary changes

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16
Q

Why are SDH common in the elderly?

A

Brain shrinks with age so there is more natural space between the brain and dura mater

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17
Q

What is an intracerebral haematoma and what are its characteristics?

A

Bleeding within the brain itself usually within the white matter of frontal and temporal lobes
Related to poor outcomes and high morbidity
Dilated pupil on side of the lesion and hemiplegia on the opposite side to the lesion

18
Q

What are contusions and what are their characteristics?

A

Bruising in the brain
Not necessarily associated with severe injury - relatively common
Common in those on blood thinning medication - particularly warfrin and anti platelet medication
Often found in frontal and temporal lobes

19
Q

What are coup and contracoup injuries?

A

Coup - Found at site of impact

Contracoup - Found at opposite side to impact, caused by deceleration

20
Q

What is a subarachnoid haemorrhage and what are its characteristics?

A

Bleeding below the arachnoid layer

High risk of developing hydrocephalus due to blocked arachnoid villi

21
Q

What occurs at a cellular level during a simple disturbance such as concussion?

A

Axonal injury -> electrochemical discharge due to Ca2+ influx or some proteins sensing stretch of the axon -> release of NT into the synapse

22
Q

Other than axonal stretch what other cellular effects are seen during TBI?

A

Damage to microtubules in axon cytoskeleton - impaired axonal transmission as compounds can be transported along the axon
Migration of inflammatory cells around the nerve sheeth - response from microglia and external inflammatory cells, attracted by leak of DAMPs and cytokines from damaged cells

23
Q

What is the significance of raised ICP?

A

Blood flow is impeded by raised ICP, when brain pressure > capillary pressure, perfusion stops
Sustained and uncontrolled rises in ICP are normally fatal

24
Q

Mechanisms leading to raised ICP:

A

Cytotoxic oedema - ischaemia, direct neural disruption
Vasogenic oedema - blood brain barrier injury
CSF volume
Haemamtoma
Raised cerebral blood volume

25
Q

How does an ischaemic injury occur in TBI?

A

Brain has a high metabolic demand as it is unable to store energy and required a constant supply of O2 and glucose to generate ATP.
If hypoperfusion is maintained then there will be death of some brain cells

26
Q

How would a graph of ICP against volume look like and why?

A

Initially flat/slow rise but then becomes exponential

Initially there is not a rise in ICP as volume increases but as compensatory mechanisms are exhausted there is a sharp rise in ICP

27
Q

Why is the shape of the ICP Volume curve useful?

A

The curve works in reverse meaning even small interventions such as analgesia or straightening the neck can have a large effect on reducing ICP

28
Q

Why is ICP still lowered despite no studies showing it improves outcomes?

A

One of the few things that can be controlled and treated

There are some scenarios where ICP can’t be allowed to rise as it would be certainly fatal

29
Q

Measures to control ICP:

A 
Control fever
Control seizures
Manipulate blood pressure
Manage electrolyte levels
Levels of sedation and analgesia
30
Q

Why does coma occur?

A

Due to functional damage not a protective response

31
Q

What occurs when the brain is damage by an impact?

A

Area of the brain directly damaged by impact - area is not dead but is profoundly affected and prone to swelling
As the area swells it pushes on adjacent areas which then become ischaemic and damage propagates to further areas.

32
Q

How does stretching the axon result in Injury?

A

The axon stretched causing the opening of mechanical Ca2+ channels leading to an influx of Ca2 and depolarisation. This opens voltage gated Ca2+ channels
and causes further Ca2+ influx and depolarisation. Mitochondria become overloaded with Ca2+ leading to the mitochondria stop working and the production of oxygen free radicals. Ca2+ influx also activates lipase and proteases via secondary messengers causing cell digestion.

Stretching the axon also damages microtubules, reducing axon transport which causes glutamate release which further increases Ca2+ influx

33
Q

How does the brain control its own blood supply and why can this be used in TBI treatment?

A

There is normally a zone of autoregulation where an increase in BP leads to vasoconstriction and so reduces blood volume entering the brain which in turn will reduce ICP - however sometimes this mechanism is compromised in TBI and an increase in BP leads to an increase in ICP

34
Q

Why does sedation cause ICP to fall?

A

It relaxes muscles so venous return from the brain isn’t affected which reduces blood volume in the brain and so lowers ICP

35
Q

What are second line therapies for increasing ICP?

A

Manipulate BP
Therapeutic hypothermia
Decompressive surgery
Deep coma

36
Q

What is the trade off with decompressive surgery?

A

Increases the rate of survival but at the expense of increased disability

37
Q

What is the effect of TXA on TBI?

A

Shows a significant reduction in mortality for mild to moderate injury but there are less clear effects for those with severe injuries

38
Q

What is concussion?

A

A transient impairment of neurological function after mechanical injury

39
Q

Why are mTBI likely to be under reported?

A

Most patients have a spontaneous resolution of symptoms even in the absence of medical care

40
Q

Repeated concussion is associated with

A

Depression, Chronic neurodegenerative conditions later in life - Parkinson’s disease, motor neuron disease

41
Q

Why don’t mTBI show up on scans?

A

Don’t typically cause structural injury to the brain

Neurotrauma (4 decks)

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