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Clinical neuroscience > Raised intracranial pressure > Flashcards

Raised intracranial pressure Flashcards

1
Q

What determines normal ICP?

A
  • Determined by volume of blood, brain and CSF, also enclosed in a rigid box
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2
Q

What are the normal values for ICP?

A
  • Adults 5-15 mmHg
  • Children 5-7 mmHg
  • Term infants 1.5-6 mmHg
  • A good rule of thumb is that a pressure >20 mmHg is raised
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3
Q

What is the Monro-Kellie doctrine?

A
  • Any increase in the volume of one of the intracranial constituents (brain, blood, or CSF) must be compensated by a decrease in the volume of one of the others
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4
Q

What happens in the case of an intracranial mass?

A
  • The first components to be pushed out of the intracranial space are CSF and venous blood, since they are at the lowest pressure
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5
Q

How do we calculate cerebral perfusion pressure?

A
  • Mean arterial pressure - ICP
  • Normal CPP >70 mmHg
  • Normal MAP ~90 mmHg
  • Normal ICP ~10 mmHg
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6
Q

What happens when mean arterial pressure increases?

A
  • Cerebral perfusion pressure increases
  • Triggers cerebral autoregulation to maintain cerebral blood flow
  • Vasoconstriction
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7
Q

What happens if ICP increases?

A
  • Cerebral perfusion decreases
  • Triggers cerebral autoregulation to maintain cerebral blood flow
    Vasodilation
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8
Q

What happens if CCP is greater than 50 mmHg?

A
  • Cerebral blood flow cannot be maintained as cerebral arterioles are maximally dilated
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9
Q

What happens to ICP as an intracranial mass expands?

A
  • ICP can initially be maintained at a constant level up to a certain point
  • After this point ICP will rise at a very rapid (exponential rate)
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10
Q

What can damage to the brain cause?

A
  • Impairment or abolishment of cerebral autoregulation
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11
Q

What is Cushing’s reflex?

A
  • A rise in ICP will initially lead to hypertension
  • Bradycardia
  • Irregular breathing
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12
Q

Why does a rise in ICP initially lead to hypertension?

A
  • The body increases mean arterial pressure to maintain cerebral perfusion pressure
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13
Q

Why does an increase in ICP result in bradycardia?

A
  • The corresponding increase in MAP is detected by baroreceptors which stimulate a reflex bradycardia via increased vagal activity (can cause stomach ulcers as a dangerous side effect)
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14
Q

Why does raised ICP result in irregular breathing?

A
  • Continuing compression of the brainstem leads to damage to respiratory centres causing irregular breathing
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15
Q

What are the causes of raised ICP?

A
  • Too much blood within cerebral vessels (rare)
  • Too much blood outside of cerebral vessels (haemorrhage)
  • Too much CSF
  • Too much brain
  • Something else e.g. tumour, cerebral abscesses, idiopathic
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16
Q

What causes too much blood within cerebral vessels?

A
  • Raised arterial pressure (malignant hypertension)
  • Raised venous pressure (SVC obstruction e.g. by a lung tumour)
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17
Q

What causes too much blood outside of cerebral vessels?

A
  • Extradural
  • Subdural
  • Subarachnoid
  • Haemorrhagic stroke
  • Intraventricular haemorrhage
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18
Q

What are some causes of too much CSF?

A
  • Hydrocephalus
  • Acquired
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19
Q

What are the causes of hydrocephalus?

A
  • Congenital (more common than acquired types)
  • Obstructive e.g. neural tube defects, aqueduct stenosis
  • Frequently part of a larger syndrome
  • Communicating e.g. increased CSF production or decreased CSF absorption
20
Q

What are the clinical signs of hydrocephalus?

A
  • Bulging with head circumference increasing faster than expected
  • Sunsetting eyes (due to direct compression of orbits as well as involvement of oculomotor nerve as it exits the midbrain)
21
Q

How is hydrocephalus managed in the short term?

A
  • Can be treated in the acute setting by tapping the fontanelle with a needle
22
Q

How is hydrocephalus managed in the medium term?

A
  • External ventricular drain
  • Allows continuous pressure monitoring
  • Can be at risk of infection due to direct communication between brain and outside world
  • Requires inpatient monitoring so not good as a long term solution
  • Used if shunt fails or contraindicated
23
Q

How is hydrocephalus managed in the short term?

A
  • Ventricular shunts
24
Q

How are ventricular shunts inserted?

A
  • A tube is placed from the ventricular system into the peritoneum (V-P) or right atrium (V-A)
  • V-P shunts performed most commonly
  • Tube is tunnelled under skin
  • A one way valve is incorporated to prevent backflow into the ventricle
  • Extra length of tubing is provided to allow growth before revision is required
25
Q

What are V-P shunts vulnerable to?

A
  • Infection
  • Kinking
26
Q

What are some acquired causes of hydrocephalus?

A
  • Meningitis
  • Trauma
  • Haemorrhage
  • Tumours compressing cerebral aqueduct
27
Q

What are the four major pathologies of cerebral oedema?

A
  • Vasogenic - breakdown of tight junctions
  • Cytotoxic - damage to brain cells
  • Osmotic - e.g. if ECF becomes hypotonic
  • Interstitial - flow of CSF across ependyma and damage to BBB
28
Q

What are the idiopathic causes of raised ICP?

A
  • Idiopathic intracranial hypertension
29
Q

Outline idiopathic intracranial hypertension

A
  • May present with headache and visual disturbances
  • Usually obese middle aged females
  • Poorly understood aetiology
  • Diagnosis confirmed by raised opening pressure on an LP
  • Treat with weight loss and blood pressure control
30
Q

Why do we need to make sure there are no signs of intracranial pathology before doing an LP in a patient with suspected ICP?

A
  • This can precipitate brain herniation
31
Q

What are the clinical features of hydrocephalus?

A
  • Headache
  • Nausea and vomiting
  • Difficulty concentrating or drowsiness
  • Confusion
  • Double vision
  • Focal neurological signs
  • Seizures
32
Q

What is headache caused by hydrocephalus like?

A
  • Constant
  • Worse in the morning
  • Worse on bending and straining
33
Q

What is double vision due to hydrocephalus like?

A
  • Problems with accommodation (early sign)
  • Pupillary dilation (late sign)
  • May be effects on acuity
  • Visual field defects
  • Papilledema
34
Q

What is tonsillar herniation?

A
  • Cerebellar tonsils herniate through foramen magnum, compressing medulla
35
Q

What is subfalcine herniation?

A
  • Cingulate gyrus is pushed under the free edge of the falx cerebri
  • Can compress anterior cerebral artery as it loops over the corpus callosum
36
Q

What is uncal herniation?

A
  • Uncus of temporal lobe herniates through tentorial notch, compressing adjacent midbrain
  • Can cause third nerve palsy and maybe even contralateral hemiparesis (due to compression of cerebral peduncle)
37
Q

What is central downward herniation?

A
  • Medial temporal lobe /other midline structures pushed down through tentorial notch
38
Q

How is hydrocephalus managed?

A
  • Brain protection measures
  • Other treatments
39
Q

How do we protect the brain?

A
  • Airway and breathing
  • Circulatory support
  • Sedation, analgesia and paralysis
  • Head up tilt
  • Temperature
  • Anticonvulsants
  • Nutrition and proton pump inhibitors
40
Q

What are the airway and breathing brain protection measures used to treat hydrocephalus?

A
  • Maintain oxygenation and removal of CO2
41
Q

What are the circulatory protection measures used to treat hydrocephalus?

A
  • Maintain mean arterial pressure and hence CPP
42
Q

What are the sedation, analgesia and paralysis protection measures used to treat hydrocephalus?

A
  • Used to decrease metabolic demand
  • Prevents cough/shivering that might increase ICP further
43
Q

Why do we do a head tilt in a patient with hydrocephalus?

A
  • Improves cerebral venous drainage
44
Q

Why do we need to control a patient’s temperature with hydrocephalus?

A
  • Prevent hyperthermia
  • Therapeutic hypothermia may be beneficial
45
Q

Why does a patient with hydrocephalus need anticonvulsants?

A
  • Prevent seizures
  • Also need to reduce metabolic demand
46
Q

Why does a patient with hydrocephalus need nutrition and PPIs?

A
  • Improved healing of injuries and prevent stomach ulcers due to increased vagal activity
47
Q

What are some other treatments of hydrocephaly?

A
  • Mannitol or hypertonic saline (osmotic diuresis)
  • Ventricular drainage
  • Decompressive craniectomy as a last resort

Clinical neuroscience (19 decks)

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