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Head and Neck Pathology > Intracranial Pressure and Brain Injury > Flashcards

Intracranial Pressure and Brain Injury Flashcards

1
Q

What are the major components of ICP?

A

brain
CSF
blood
> increased volume of any one will raise ICP, unless compensatory reduction in one/both of other components
> if ICP continues to increase, compensatory mechanisms will fail

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2
Q

Describe compensatory mechanism in intracranial pressure?

A
  1. reduction in the CSF space > within and around the brain
  2. pressure atrophy of the brain > which occurs most commonly with slow-growing extrinsic lesions, e.g. meningiomas
  3. reduction in blood volume e.g. within the intracranial venous sinuses
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3
Q

What are the consequences of intracranial space-occupying lesions?

A
  1. raised intracranial pressure
  2. intracranial shift and herniation
  3. epilepsy
  4. hydrocephalus
  5. systemic effects
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4
Q

What are the characteristic clinical signs and symptoms of raised intracranial pressure?

A
  1. papilloedema: due to accumulation of axoplasm in optic papilla
  2. nausea and vomiting: due to pressure on vomiting centres in the pons and medulla
  3. headache: due to compression and distortion of pain and stretch receptors
  4. impairment of consciousness, ranging from drowsiness to deep coma, related to the level of increased intracranial pressure
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5
Q

What are the common causes of raised ICP?

A
  1. intracranial expanding lesions (“space-occupying lesions”) – e.g. tumour, haematoma, abscess
  2. hydrocephalus (excess CSF)
  3. cerebral oedema – increase in brain water content, due to blood-brain barrier problem
    > localised (e.g. around tumours)
    > generalised (e.g. following severe head injury or hypoxic brain damage)
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6
Q

Name the sites of brain herniation?

A
  1. subfalcine
  2. (trans)tentorial
  3. tonsillar
  4. also through skull defect in trauma or before sutures fuse
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7
Q

Describe decompensation?

A

causes shifts and herniation

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8
Q

What is Cushing reflex?

A

a physiological nervous system response to acute elevation of intracranial pressure resulting in Cushing triad of
1. widened pulse pressure (increasing systolic, decreasing diastolic)
2. bradycardia
3. irregular respirations
> haemodynamic changes
(raised BP, slowed pulse)

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9
Q

What causes a subfalcine herniation?
(=supracallosal or cingulate hernia)

A
  • usually due to primary abnormality in one cerebral hemisphere
  • ipsilateral cingulate gyrus herniates under the free edge of falx
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10
Q

What arteries are affected by a subfalcine herniation?

A
  1. pericallosal arteries are compressed > possible cerebral infarction
  2. anterior cerebral artery may also be affected > larger infarct
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11
Q

Describe a tentorial herniation?

A
  1. medial aspect of temporal lobe through tentorium
    > affects hippocampus
  2. midbrain compressed and distorted
    > compressed aqueduct impairs CSF flow (obstructive hydrocephalus)
    > haemorrhage in pons and midbrain
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12
Q

Tentorial herniation poses a risk to what structures?

A
  1. ipsilateral 3rd nerve
  2. posterior cerebral artery
  3. opposite cerebral peduncle
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13
Q

Describe tonsillar herniation?

A
  • cerebellar tonsils move down – with medulla form “cone” shape
  • exit from 4th ventricle blocked impairing CSF flow (obstructive hydrocephalus)
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14
Q

Clinical consequences of tonsillar herniation?

A

compression of breathing and cardiac centres in medulla
> causing Cushing reflex and even death

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15
Q

What is the effect of transtentorial herniation?

A

Ipsilateral 3rd cranial nerve compression
Ipsilateral 6th cranial nerve compression
Posterior cerebral artery compression
Cerebral peduncle compression
Brainstem compression and haemorrhage

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16
Q

What is the clinical consequence of transtentorial herniation?

A

Ipsilateral fixed dilated pupil
Horizontal diplopia, convergent squint
Occipital infarction
Cortical blindness
Upper motor neurone signs
Decerebrate posture
Cardiorespiratory failure
Death

17
Q

What is the effect of the foramen magnum herniation?

A

Brainstem compression and hemorrhage
Acute obstruction of CSF pathway

18
Q

What is the clinical consequence of foramen magnum herniation?

A

Decerebrate posture
Cardiorespiratory failure
Death

19
Q

Lumbar puncture (LP) is dangerous and should be avoided if ICP raised. Why?

A

high risk of herniation

20
Q

Is there any way you might check for raised ICP before doing an LP?

A

CT scan or MRI

21
Q

Types of traumatic brain injury?

A

missile or (more commonly) non-missile injury

22
Q

Describe types of non missile traumatic brain injury?

A
  1. primary – focal lesions (contusion/tear) or diffuse axonal injury
  2. secondary – e.g. traumatic vascular injury with intracranial haematoma, oedema, herniation, infarction, hydrocephalus, infection
23
Q

What are the clinical effects of non-missile traumatic brain injury?

A
  1. minor - concussion
  2. major – e.g. death, epilepsy, persistent vegetative state (PVS), post traumatic dementia
24
Q

Name types of cerebral contusions?

A
  1. coup
  2. contre coup
25
Q

What is a coup contusion?

A

injury occcurs immediately under the site of impact with an object

26
Q

What is a contre coup contusion?

A

injury that occurs on the site opposite the area that was hit

27
Q

Describe diffuse axonal injury?

A

Shearing and tearing of the brains axons that happens when the brain is injured as it shifts and rotates inside the bony skull
- particularly in deep white matter
- even with very minor trauma

28
Q

Consequences of diffuse axonal trauma?

A
  • axonal swelling and focal haemorrhage
  • contribute to cerebral oedema and raised ICP
    > long term effects variable
29
Q

What are types of traumatic vascular injury?

A
  1. extradural
  2. subdural
  3. subarachnoid and intracerebral
30
Q

Describe extradural (epidural) traumatic vascular injury?

A

especially injury to middle meningeal artery

31
Q

Describe subdural traumatic vascular injury?

A

Dural veins > shearing stress
acute or chronic (recurrent bleeding)
more common in the elderly and in any bleeding diathesis
injury often trivial /missed

32
Q

Describe subarachnoid and intercerebral traumatic vascular injury?

A

In trauma, usually secondary to contusions

33
Q

Compare extradural and subdural hematomas?

A
34
Q

Describe the cause of spinal cord trauma and it’s consequences?

A

Cause
• a most often due to accidents and displacement of vertebral column + /- vascular problem
• cord/nerve root compression, transection etc
Consequences
• effects depend on site and severity
• paraplegia, quadriplegia, respiratory compromise.

Head and Neck Pathology (4 decks)

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