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B3 CTB > Head Trauma and Intracranial Pressure > Flashcards

Head Trauma and Intracranial Pressure Flashcards

1
Q

What is head trauma?

A

Anything that results in damage to the head that can lead to raised intracranial pressure and changes in consciousness.

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2
Q

What can cause head trauma?

A
  • Skull fractures.
  • Knocks to the head causing concussion.
  • Haemorrhage.
  • Tumours.
  • Expanding lesions e.g. abscess, cysts, meningitis etc.
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3
Q

Brain is very well protected by the ?, ? (supports the brain and acts as a shock absorber) and ? (double layers of meninges which keep the cerebral hemispheres in place).

A

skull
CSF
dura septa

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4
Q

What does increased ICP often result in?

A

Compression of the brain and herniation of key parts of the brain.

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5
Q

What is the normal range of ICP?

A

0 - 10 mmHg

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6
Q

What is the volume of the skull?

A

Around 1700 ml

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7
Q

What fills the cranium and in what preportions?

A

Brain accounts for around 80% of the space.
Cerebrospinal fluid around 10%.
Blood supply around 10%.

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8
Q

What is the Monro-Kellie Hypothesis?

A

The sum of the volumes of the brain (80), CSF (10) and intracranial blood (10) is constant (in equilibrium). An increase in one should result in a decrease in the other two.

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9
Q

What equation represents the Monro-Kellie Hypothesis (V = Volume)?

A

Vtotal = Vbrain + Vblood + VCSF + Vmass

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10
Q

What first occurs if a mass begins to develop and enlarge in the cranial vault?

A

Compensatory mechanisms initiated to keep the brain in optimal condition.

CSF is shunted to cisterns surrounding base of the brain and spinal cord.

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11
Q

Give an example of two masses that could develop in the cranial vault.

A

Haemorrhage or tumour.

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12
Q

What is the lumbar cistern?

A

CSF filled space at the bottom of the spinal cord where a lumbar puncture is directed as the spinal cord stops at L2.

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13
Q

What is the cisterna magna?

A

CSF-filled gap between the cerebellum and the medulla, finishing as the cord exits the foramen magnum.

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14
Q

If a mass in the cranium continues to grow, what can happen (after CSF has been shunted into cisterns)?

A

Blood vessels start to compress.

Huge risk of damage as the perfucion to the distal regions of the brain may drop below the levels needed.

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15
Q

Any ICP greater than ? mmHg requires intervention.

A

20

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16
Q

Keeping a constant supply of blood is key to maintaining the health of brain tissue. It needs a constant supply of ? and ? to function.

A

glucose, oxygen

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17
Q

How can you regulate the cerebral perfusion pressure (CPP)?

A

By changing the volume of blood and vessel resistance.

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18
Q

Normal vertebral perfusion pressure is usually maintained at ? mmHg.

A

50 - 70

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19
Q

How do you calculate CPP?

A

CPP = MAP - ICP

Cerebral perfusion pressure = mean arterial pressure - intracranial pressure

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20
Q

How do you increase CPP?

A

Increase MAP or decrease ICP.

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21
Q

How do you detect raised ICP?

A
  • Headache.
  • Localising signs.
  • Change in consciousness.
  • Papilloedema.
  • Fixed dilated pupil
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22
Q

What are localising signs?

A

Signs and symptoms that indicate which region of the brain has been injured.

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23
Q

What is papilloedema?

A

Optic disc appears to be bulging out of the vitreous body as a result of movement of CSF into the subarachnoid space surrounding the optic nerve.

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24
Q

What sign can precede papilloedema to indicate raised ICP?

A

A dilated pupil in one eye that becomes fixed.

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25
Q

Why might a raised ICP cause fixed pupil dilation?

A

An increase ICP can compress the Oculomotor nerve against the septa, resulting in a loss of parasympathetic supply to the eye (parasympathetic fibres wrap around the CN as it travels to the eye.

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26
Q

A patient is brought in with suspected meningitis. The GCS is reducing and CT shows meningeal enhancement. Do you perform a lumbar puncture?

A

No. Meningeal enhancement suggests significant infection and irritation of the meninges.

Decreasing consciousness would suggest ICP is increasing and there is a risk of coning is a lumbar puncture is performed.

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27
Q

What is herniation of the brain?

A

Movement of brain tissue around the fixed/rigid objects inside the skull (cranial vault), resulting in compression and damage to the tissue as it passes over/under these obstacles.

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28
Q

Where is herniation most likely to occur?

A

Foramen magnum (large hole)

Dural septa (fixed structure)

Falx cerebri

Tentorium cerebelli

29
Q

What is a subfalcine hernia?

A

Caused by movement of cerebral tissue (usually the cingulate gyrus) downwards and underneath the falx cerebri.

30
Q

What is a transtentorial (uncal) hernia?

A

Movement of the uncus over the edge of the tentorium cerebelli (into the tentorial notch).

31
Q

What is the uncus?

A

The hook of tissue protruding fro the medial temporal lobe.

32
Q

What nerve can an uncal herniation trap?

A

Oculomotor nerve - unilateral pupil dilation can often indicate the onset of increasing ICP.

33
Q

What is a tonsillar herniation?

A

Forced downwards movement of the cerebellar tonsils pushing them out through the foramen magnum.

34
Q

What is central herniation?

A

Movement of the deeper cerebral tissue to the contralateral side and downwards towards the gap created by the tentorium.

35
Q

What can central herniation cause?

A

Increased pressure on the brainstem and cerebellum and coning.

36
Q

What is transcalvarial herniation?

A

Extrusion of brain tissue through a break in the skull.

37
Q

How can trancalvarial herniation be utilised in neurosurgery?

A

To reduce the impact of swelling by removing the skull and allowing the brain to swell and recede before replacing the bone.

38
Q

Tentorial herniation can cause significant damage to the ?, which connects the frontal lobe to the temporal lobe, leading to behavioural changes.

A

:uncinate fasciculus

39
Q

What is Kernohan’s notch?

A

A fold in the cerebral pedubcle (midbrain) that forms as a result of tissue moving (usually part of a transtentorial herniation) from one side of the skull to another, causing the peduncle to fold on itself.

Fold can result in contralateral motor deficits as it impacts on the CSTs.

40
Q

What is coning?

A

The forced movement and herniation of the brainstem through the foramen magnum, crushing the vital cardiovascular, respiratory and consciousness centres and is a medical emergency.

41
Q

What is Chiari malformation?

A

A congenital disorder where the cerebellar tonsils project into the foramen magnum.

42
Q

Head injury results in the brain being shaken inside the skull. This causes direct injury to the brain, resulting in ? or ? due to rupture of arteries or veins.

A

oedema, haemorrhage

43
Q

Why is CT imaging the quickest way to detect a haemorrhage?

A

Fresh blood is bright compared to grey tissues.

44
Q

What are the four types of haemorrhage?

A
  1. Extradural/ epidural.
  2. Subdural.
  3. Subarachnoid.
  4. Intracerebral/intraparenchymal.
45
Q

What usually causes an epidural haemorrhage?

A

Trauma to the head ruptures meningeal arteries.

Causes blood to accumulate between the wall of the skull and the dura mater (epidural space).

46
Q

Epidural haemorrhages usually occur due to bleeding from the ? artery (branch of the ?).

A

middle meningeal, external carotid

47
Q

Why is the pterion of the skull particularly susceptible to fracture (behind temple)?

A

Where the frontal, parietal, temporal and sphenoid bones fuse.

Significant trauma to this area can can internal dispacement of the bone.

48
Q

Why does an epidural haemorrhage have a lenticular shape on a CT scan?

A

It is compartmentalised - haematoma cannot extend beyond these fusion points so bulges inwards.

49
Q

What causes a subdural haemorrhage?

A

Blow that causes the brain to move within the skull.

Blood collects in the subdural space following the rupture of a vein.

50
Q

Which vessels are usually injured to cause a subdural haemorrhage?

A

Bridging veins

51
Q

Why does a subdural haemorrhage have a crescent-shaped haematoma?

A

Blood can spread throughout the subdural space.

52
Q

What usually causes a subarachnoid haemorrhage?

A

Rupture of a micro-aneurysm.

Blood collects in the CSF beneath the arachnoid layer of the meninges (between arachnoid and pia mater).

53
Q

What causes an intracerebral/ intraparanchymal haemorrhage?

A

Rupture of a vessel within the brain substance e.g. the internal capsule.

54
Q

Fresh blood is ? in MRI imaging.

A

isodense

55
Q

As blood degrades, it’s density changes, which means that ? becomes less useful as the haemorrhage ages.

A

CT

56
Q

How does blood appear on CT images as it ages (acute, subacute and chronic)?

A
  • Acute (<1 week): blood is bright.
  • Subacute (1 – 3 weeks): haemorrhage becomes isodense to the brain tissue (harder to detect).
  • Chronic (> 3 weeks): blood begins to break down and appears black in contrast to white bone and grey tissue.
57
Q

Epidural haemorrhages: Patients may exhibit a ? period following the initial head trauma as it takes time for the blood to build up enough pressure to detach the dura from the skull.

A

lucid

58
Q

Which group are epidural haemorrhages more common in?

A

The elderly, often fatal

59
Q

Subdural haemorrhages are characterised by a ? onset and ? decline.

A

slow progressive, cognitive

60
Q

Which groups are subdural heamorrhages more common in?

A

Elderly

61
Q

Are subarachnoid heamorrhages usually venous or arterial blood?

A

Arterial (ruptures aneurysm).

62
Q

What type of haemorrhages can fill gaps between the sulci and enter the ventricular system.

A

Subarachnoid

63
Q

What is contusion?

A

Region of tissue and blood vessel damage - a bruise.

64
Q

Where does contusion usually occur?

A

More superficial levels of the brain as the brain bumps around as a result of trauma.

65
Q

How can contusion be graded?

A
  • If it is limited to grey matter, it is mild.
  • If it involves grey and white, moderate.
  • If the haemorrhages coalesce, severe.
66
Q

Lots of scattered micro-haemorrhages in the white-grey matter border or in the white matter are often indicative of ?

A

diffuse axonal injury

67
Q

Contusion is most commonly found in the contre-cusp side of the brain, what is this?

A

The opposite side of the brain to the region of trauma.

68
Q

What is diffuse axonal injury?

A

Damage that results from a twisting or rotational force being applied to the brain e.g. in a crash.

Causes what appear to be small lesions, usually at the border of white and grey matter.

69
Q

What are the different types of herniation?

A

Subfalcine

Transtentorial

Tonsillar

Central

Transcalvarial

B3 CTB (13 decks)

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