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Medicine Year 2 > Topic 9 - Head Injuries > Flashcards

Topic 9 - Head Injuries Flashcards

1
Q

Describe the development of an intracranial haematoma

A

Following head injury, blood can gather between the meninges or within the brain - no true space in normal anatomy, increases potential space

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2
Q

Describe the ability of the CNS to recover

A
  • CNS neurons have limited ability to recover in comparison to PNS neurons
  • Substantial functional recovery occurs due to neural plasticity
    • Potential for brain to change structure and function - rewiring of neurons
    • Greater exposure to particular stimulis means more neurons are dedicated to that stimulus (+ vice versa)
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3
Q

List the types of brain injuries

A
  1. Primary injury - result of initial trauma
  2. Secondary injury - evolving pathophsysiological consequences of the primary injury
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4
Q

Describe the development of a subdural haematoma

A
  • Venous blood
  • Collects between dura and arachnoid mater
  • No limitation of blood flow, spreads more evenly
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5
Q

Describe the appearance of a subdural haematoma on a CT

A
  • No limitation of blood flow, blood can spread more evenly
  • Less clear on CT, crescent shape
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6
Q

List the clinical signs of displacement of the cingulate gyrus under the falx cerebri

A
  • May have no clinical signs
  • May be confused, drowsy or show contralateral weakness
    • Pressure on motor cortex or compression of anterior cerebral artery)
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7
Q

When does recovery from brain injuries occur?

A

Fastest recovery occurs in the first 6 months, continues for 2 years

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8
Q

Describe normal and abnormal flexion in the motor response section of the Glasgow coma scale

A

Normal - elbow bends, arm moves away from body

Abnormal - elbow bends, arm moves over body

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9
Q

Why does brain herniation develop after head injuries?

A

Brain is not compressible - as mass expands causes displacement (herniation)

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10
Q

Explain the clinical usefullness of a Glasgow Coma Score

A

Numbers from each section can be added to give score, not accurate representation of patient’s condition

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11
Q

Describe the appearance of an extradural haematoma on a CT scan

A
  • Characteristic lens shape - blood collects in one area because the dura is fixed to the skull at sutures so it can’t spread
  • Causes midline shifting - loss of ventricles
  • Fresh blood appears white, turns more grey with time
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12
Q

List the categorisation of GCS scores

A

Mild = 13-15

Moderate = 9-12

Severe = 8 or less

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13
Q

List types of secondary head injuries

A
  • Cerebral oedema
  • Increased intracranial pressure
  • Haemorrhage
  • Herniation
  • Seizures
  • Ischaemia
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14
Q

List the behavioural consequences of brain injury

A
  • Period of confusion, disorientation
  • Attention and learning ability lost
  • Agitation, agression, frustration
  • Nervousness, restlessness
  • Sleeping pattern disrupted
  • Overreaction to stimulation
  • Inconsistent behaviour
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15
Q

Describe the affect of downwards herniation of the brain on brainstem functions

A
  • Coma
  • Altered respiratory rate
  • Altered HR
  • Altered BP control
  • Death from cardiorespiratory arrest
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16
Q

Explain the effect a head injury will have on CPP

A
  • ICP increases after injury, decreasing the CPP
  • Blood flows from high to low pressure, raised ICP decreases the pressure gradient favouring blood flow to the brain
  • Normally the brain autoregulates bloodflow regardless of pressure by changing the resistance of vessels, but after injury these homeostatic mechanisms fail
  • Increasing ICP leads to decreasing CPP and ischaemic damage
17
Q

Describe the stages of brain herniation

A
  1. Displacement of cingulate gyrus from one hemisphere to another under the falx cerebri
  2. Brain moves downwards (uncle herniation)
  3. Brainstem affected
18
Q

List the types of primary injury and give examples

A
  • Focal - localised to site of impact
    • Fracture
    • Haematoma - localised bleeding outside blood vessels
  • Polar
    • Cerebral contusions - multiple microhaemorrhages, small blood vessels leak into brain tissue
    • Usually occur coup (adjacent to site of impact) or contre coup (diagonally opposite)
  • Diffuse - movements of the brain within the cranial cavity causing widespread neurol damage
    • Diffuse axonal injury - ‘stretching’ injury to the neurons + axons throughout the brain
19
Q

Describe the Glasgow Coma Scale

A
  • Eye opening
    • Spontaneous - 4
    • To sound - 3
    • To pressure - 2
    • None - 1
  • Verbal response
    • Oriented - 5
    • Confused - 4
    • Words - 3
    • Sounds - 2
    • None - 1
  • Motor response
    • Obey commands - 6
    • Localising to pain - 5
    • Normal flexion - 4
    • Abnormal flexion - 3
    • Extension - 2
    • None - 1
20
Q

Define the Glasgow Coma Scale

A

A standardised test developed for assessing the level of consciousness in acutely brain injured individual

21
Q

How is CPP used clinically?

A

As a surrogate marker for cerebral blood flow

22
Q

Describe an intracerebral haematoma

A

Blood within substance of brain

23
Q

List the types of intracranial haematomas

A
  1. Extradural/epidural
  2. Subdural
  3. Intracranial
  4. Subarachnoid
24
Q

How is ICP measured clinically?

A
  • Can be measured directly - invasive so not usually done
  • Neurological observations used to detect increasing ICP after head injuries
    • GCS
    • Vitals - pulse, BP, temperature
    • Pupil responses
    • Motor/sensory response
  • Every 15 minutes
25
Q

List the signs of increasing ICP

A
  • Decreasing GCS
  • Lack of pupillary response to light
  • Lateralising signs - weakness on L or R
26
Q

How is cerebral perfusion pressure related to intracranial pressure?

A

CPP = MAP (mean arterial pressure) - ICP

As ICP rises, CPP falls

27
Q

Describe the development of an extradural haematoma

A
  • Usually arterial bleeding, often from the middle meningeal artery
  • Blood collects between the periosteal layer of the dura and the skull
  • Periosteal dura is fixed to skull at sutures so blood can’t spread around the whole skull
28
Q

Describe the procedure used to carry out the Glasgow coma scale

A
  1. Check - identify factors which may interfere with assessment e.g. hearing impairment
  2. Observe for spontaneous behaviour
  3. Stimulate if no spontaneous response
  4. Rate
29
Q

Describe subarachnoid haematomas

A

Blood collects under arachnoid layer

30
Q

Describe uncle herniation and clinical signs

A
  • Herniation of the medial temporal lobe from middle to posterior cranial fossa across the tentorial opening
  • Uncus is compressed against midbrain - compresses oculomotor nerve
  • Parasympathetic fibres travel on outside of oculomotor nerve - fixed and dilated pupil seen before deviation of eye in down and out position
31
Q

Describe the compensatory mechanism of the brain in response to an expanding mass lesion

A
  • Compensatory capacity is limited
    • CSF - 75ml displaced into spinal theca/venous system via arachnoid granules
    • Intracranial venous blood - 75ml redistributed peripherally
    • Brain is incompressible
    • Arterial volume must remain constant - need to maintain blood supply to brain
  • Initially as mass expands, CSF and venous blood redistribution maintains ICP
  • Reaches critical point - limit of compensation reached (mass lesion >100-120ml)
  • ICP rises exponentially
32
Q

Describe the Monroe-Kellie Principle

A
  • Within the skull, there is brain (80%), CSF and blood (venous and arterial)
  • ICP must be kept constant - the skull is a rigid container which can’t expand
  • If the volume inside the skull increases, this must be offset by an equal decrease in the volume of the other components to keep the ICP constant
33
Q

List the common types of facial fracture

A
  • Zygomaticomaxillary complex (tripod) fracture
  • LeFort I, II or III
  • Zygomatic fracture
  • Orbital floor (‘blow-out’)
34
Q

Define a zygomaticomaxillary (tripod) fracture

A
  • Most common
  • Involves separation of all three major attachments of the zygomatic bone to the rest of the face
  • Can cause impingement of temporalis muscle - inability to open mouth
35
Q

Define an orbital floor fracture

A
  • Usual mechanism is a blow to the eye
  • Thin floor of orbit fractures, eye drops into maxillary sinus
36
Q

Describe LeFort fractures

A
  • LeFort I
    • Horizontal, floating palate, transmaxillary
    • Floating fragment - lower maxilla and maxillary teeth
  • LeFort II
    • Pyramidal
    • Commonly due to downwards blow to nasal area
    • Fracture through the inferior orbital floor
  • LeFort III
    • Transverse, craniofacial dissociation
    • Most severe - detachement of facial skeleton from cranium
    • Fracture through zygomatic arch

Medicine Year 2 (41 decks)

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